diff --git a/tianshou/core/mcts/unit_test/Evaluator.py b/tianshou/core/mcts/unit_test/Evaluator.py
new file mode 100644
index 0000000..a1f9456
--- /dev/null
+++ b/tianshou/core/mcts/unit_test/Evaluator.py
@@ -0,0 +1,28 @@
+import numpy as np
+
+
+class evaluator(object):
+    def __init__(self, env, action_num):
+        self.env = env
+        self.action_num = action_num
+
+    def __call__(self, state):
+        raise NotImplementedError("Need to implement the evaluator")
+
+
+class rollout_policy(evaluator):
+    def __init__(self, env, action_num):
+        super(rollout_policy, self).__init__(env, action_num)
+        self.is_terminated = False
+
+    def __call__(self, state):
+        # TODO: prior for rollout policy
+        total_reward = 0.
+        action = np.random.randint(0, self.action_num)
+        state, reward = self.env.simulate_step_forward(state, action)
+        total_reward += reward
+        while state is not None:
+            action = np.random.randint(0, self.action_num)
+            state, reward = self.env.simulate_step_forward(state, action)
+            total_reward += reward
+        return np.ones([self.action_num])/self.action_num, total_reward
diff --git a/tianshou/core/mcts/unit_test/ZOGame.py b/tianshou/core/mcts/unit_test/ZOGame.py
new file mode 100644
index 0000000..8a2ed54
--- /dev/null
+++ b/tianshou/core/mcts/unit_test/ZOGame.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+import numpy as np
+import copy
+
+
+class ZOTree:
+    def __init__(self, size):
+        self.size = size
+        self.depth = self.size * 2
+
+    def simulate_step_forward(self, state, action):
+        seq, color = copy.deepcopy(state)
+        if len(seq) == self.depth:
+            winner = self.executor_get_reward(state)
+            return None, color * winner
+        else:
+            seq.append(int(action))
+            return [seq, 0 - color], 0
+
+    def executor_get_reward(self, state):
+        seq = np.array(state[0], dtype='int16')
+        length = len(seq)
+        if length != self.depth:
+            raise ValueError("The game is not terminated!")
+        result = np.sum(seq)
+        if result > 0:
+            winner = 1
+        elif result < 0:
+            winner = -1
+        else:
+            winner = 0
+        return winner
+
+    def executor_do_move(self, state, action):
+        seq, color = state
+        if len(seq) == self.depth:
+            return False
+        else:
+            seq.append(int(action))
+            if len(seq) == self.depth:
+                return False
+            return True
+
+    def v_value(self, state):
+        seq, color = state
+        choosen_result = np.sum(np.array(seq, dtype='int16'))
+        if color == 1:
+            if choosen_result > 0:
+                return 1
+            elif choosen_result < 0:
+                return -1
+            else:
+                return 0
+        elif color == -1:
+            if choosen_result > 1:
+                return 1
+            elif choosen_result < 1:
+                return -1
+            else:
+                return 0
+        else:
+            raise ValueError("Wrong color")
+
+if __name__ == "__main__":
+    size = 2
+    game = ZOTree(size)
+    seq = [1, -1, 1, 1]
+    result = game.executor_do_move([seq, 1], 1)
+    print(result)
+    print(seq)
\ No newline at end of file
diff --git a/tianshou/core/mcts/unit_test/agent.py b/tianshou/core/mcts/unit_test/agent.py
new file mode 100644
index 0000000..1bffdd0
--- /dev/null
+++ b/tianshou/core/mcts/unit_test/agent.py
@@ -0,0 +1,27 @@
+#!/usr/bin/env python
+import numpy as np
+import ZOGame
+import Evaluator
+from mcts import MCTS
+
+temp = 1
+
+
+class Agent:
+    def __init__(self, size, color):
+        self.size = size
+        self.color = color
+        self.simulator = ZOGame.ZOTree(self.size)
+        self.evaluator = Evaluator.rollout_policy(self.simulator, 2)
+
+    def gen_move(self, seq):
+        if len(seq) >= 2 * self.size:
+            raise ValueError("Game is terminated.")
+        mcts = MCTS(self.simulator, self.evaluator, [seq, self.color], 2)
+        mcts.search(max_step=50)
+        N = mcts.root.N
+        N = np.power(N, 1.0 / temp)
+        prob = N / np.sum(N)
+        print("prob: {}".format(prob))
+        action = int(np.random.binomial(1, prob[1]) * 2 - 1)
+        return action
\ No newline at end of file
diff --git a/tianshou/core/mcts/unit_test/game.py b/tianshou/core/mcts/unit_test/game.py
new file mode 100644
index 0000000..7ac044c
--- /dev/null
+++ b/tianshou/core/mcts/unit_test/game.py
@@ -0,0 +1,37 @@
+import ZOGame
+import agent
+
+
+if __name__ == '__main__':
+    print("Our game has 2 players.")
+    print("Player 1 has color 1 and plays first. Player 2 has color -1 and plays following player 1.")
+    print("Both player choose 1 or -1 for an action.")
+    size = 1
+    print("This game has {} iterations".format(size))
+    print("If the final sequence has more 1 that -1, player 1 wins.")
+    print("If the final sequence has less 1 that -1, player 2 wins.")
+    print("Otherwise, both players get 0.\n")
+    game = ZOGame.ZOTree(size)
+    player1 = agent.Agent(size, 1)
+    player2 = agent.Agent(size, -1)
+
+    seq = []
+    print("Sequence is {}\n".format(seq))
+    while True:
+        action1 = player1.gen_move(seq)
+        print("action1 is {}".format(action1))
+        result = game.executor_do_move([seq, 1], action1)
+        print("Sequence is {}\n".format(seq))
+        if not result:
+            winner = game.executor_get_reward([seq, 1])
+            break
+        action2 = player2.gen_move(seq)
+        print("action2 is {}".format(action2))
+        result = game.executor_do_move([seq, -1], action2)
+        print("Sequence is {}\n".format(seq))
+        if not result:
+            winner = game.executor_get_reward([seq, 1])
+            break
+
+    print("The choice sequence is {}".format(seq))
+    print("The game result is {}".format(winner))
\ No newline at end of file
diff --git a/tianshou/core/mcts/unit_test/mcts.py b/tianshou/core/mcts/unit_test/mcts.py
new file mode 100644
index 0000000..1251d05
--- /dev/null
+++ b/tianshou/core/mcts/unit_test/mcts.py
@@ -0,0 +1,198 @@
+import numpy as np
+import math
+import time
+
+c_puct = 5
+
+class MCTSNode(object):
+    def __init__(self, parent, action, state, action_num, prior, inverse=False):
+        self.parent = parent
+        self.action = action
+        self.children = {}
+        self.state = state
+        self.action_num = action_num
+        self.prior = np.array(prior).reshape(-1)
+        self.inverse = inverse
+
+    def selection(self, simulator):
+        raise NotImplementedError("Need to implement function selection")
+
+    def backpropagation(self, action):
+        raise NotImplementedError("Need to implement function backpropagation")
+
+    def valid_mask(self, simulator):
+        pass
+
+class UCTNode(MCTSNode):
+    def __init__(self, parent, action, state, action_num, prior, mcts, inverse=False):
+        super(UCTNode, self).__init__(parent, action, state, action_num, prior, inverse)
+        self.Q = np.zeros([action_num])
+        self.W = np.zeros([action_num])
+        self.N = np.zeros([action_num])
+        self.c_puct = c_puct
+        self.ucb = self.Q + self.c_puct * self.prior * math.sqrt(np.sum(self.N)) / (self.N + 1)
+        self.mask = None
+        self.elapse_time = 0
+        self.mcts = mcts
+
+    def selection(self, simulator):
+        head = time.time()
+        self.valid_mask(simulator)
+        self.mcts.valid_mask_time += time.time() - head
+        action = np.argmax(self.ucb)
+        if action in self.children.keys():
+            self.mcts.state_selection_time += time.time() - head
+            return self.children[action].selection(simulator)
+        else:
+            self.children[action] = ActionNode(self, action, mcts=self.mcts)
+            self.mcts.state_selection_time += time.time() - head
+            return self.children[action].selection(simulator)
+
+    def backpropagation(self, action):
+        action = int(action)
+        self.N[action] += 1
+        self.W[action] += self.children[action].reward
+        for i in range(self.action_num):
+            if self.N[i] != 0:
+                self.Q[i] = (self.W[i] + 0.) / self.N[i]
+        self.ucb = self.Q + c_puct * self.prior * math.sqrt(np.sum(self.N)) / (self.N + 1.)
+        if self.parent is not None:
+            if self.inverse:
+                self.parent.backpropagation(-self.children[action].reward)
+            else:
+                self.parent.backpropagation(self.children[action].reward)
+
+    def valid_mask(self, simulator):
+        # let all invalid actions be illegal in mcts
+        if not hasattr(simulator, 'simulate_get_mask'):
+            pass
+        else:
+            if self.mask is None:
+                self.mask = simulator.simulate_get_mask(self.state, range(self.action_num))
+            self.ucb[self.mask] = -float("Inf")
+
+# Code reserved for Thompson Sampling
+class TSNode(MCTSNode):
+    def __init__(self, parent, action, state, action_num, prior, method="Gaussian", inverse=False):
+        super(TSNode, self).__init__(parent, action, state, action_num, prior, inverse)
+        if method == "Beta":
+            self.alpha = np.ones([action_num])
+            self.beta = np.ones([action_num])
+        if method == "Gaussian":
+            self.mu = np.zeros([action_num])
+            self.sigma = np.zeros([action_num])
+
+
+class ActionNode(object):
+    def __init__(self, parent, action, mcts):
+        self.parent = parent
+        self.action = action
+        self.children = {}
+        self.next_state = None
+        self.next_state_hashable = None
+        self.state_type = None
+        self.reward = 0
+        self.mcts = mcts
+
+    def selection(self, simulator):
+        head = time.time()
+        self.next_state, self.reward = simulator.simulate_step_forward(self.parent.state, self.action)
+        self.mcts.simulate_sf_time += time.time() - head
+        if self.next_state is None: # next_state is None means that self.parent.state is the terminate state
+            self.mcts.action_selection_time += time.time() - head
+            return self
+        head = time.time()
+        self.next_state_hashable = simulator.simulate_hashable_conversion(self.next_state)
+        self.mcts.hash_time += time.time() - head
+        if self.next_state_hashable in self.children.keys(): # next state has already visited before
+            self.mcts.action_selection_time += time.time() - head
+            return self.children[self.next_state_hashable].selection(simulator)
+        else: # next state is a new state never seen before
+            self.mcts.action_selection_time += time.time() - head
+            return self
+
+    def expansion(self, prior, action_num):
+        self.children[self.next_state_hashable] = UCTNode(self, self.action, self.next_state, action_num, prior,
+                                                          mcts=self.mcts, inverse=self.parent.inverse)
+
+    def backpropagation(self, value):
+        self.reward += value
+        self.parent.backpropagation(self.action)
+
+class MCTS(object):
+    def __init__(self, simulator, evaluator, start_state, action_num, method="UCT",
+                 role="unknown", debug=False, inverse=False):
+        self.simulator = simulator
+        self.evaluator = evaluator
+        self.role = role
+        self.debug = debug
+        prior, _ = self.evaluator(start_state)
+        self.action_num = action_num
+        if method == "":
+            self.root = start_state
+        if method == "UCT":
+            self.root = UCTNode(None, None, start_state, action_num, prior, mcts=self, inverse=inverse)
+        if method == "TS":
+            self.root = TSNode(None, None, start_state, action_num, prior, inverse=inverse)
+        self.inverse = inverse
+
+        # time spend on each step
+        self.selection_time = 0
+        self.expansion_time = 0
+        self.backpropagation_time = 0
+        self.action_selection_time = 0
+        self.state_selection_time = 0
+        self.simulate_sf_time = 0
+        self.valid_mask_time = 0
+        self.hash_time = 0
+
+    def search(self, max_step=None, max_time=None):
+        step = 0
+        start_time = time.time()
+        if max_step is None:
+            max_step = int("Inf")
+        if max_time is None:
+            max_time = float("Inf")
+        if max_step is None and max_time is None:
+            raise ValueError("Need a stop criteria!")
+
+        while step < max_step and time.time() - start_time < max_step:
+            sel_time, exp_time, back_time = self._expand()
+            self.selection_time += sel_time
+            self.expansion_time += exp_time
+            self.backpropagation_time += back_time
+            step += 1
+        if self.debug:
+            file = open("mcts_profiling.log", "a")
+            file.write("[" + str(self.role) + "]"
+                       + " sel " + '%.3f' % self.selection_time + "  "
+                       + " sel_sta " + '%.3f' % self.state_selection_time + "  "
+                       + " valid " + '%.3f' % self.valid_mask_time + "  "
+                       + " sel_act " + '%.3f' % self.action_selection_time + "  "
+                       + " hash " + '%.3f' % self.hash_time + "  "
+                       + " step forward " + '%.3f' % self.simulate_sf_time + "  "
+                       + " expansion  " + '%.3f' % self.expansion_time + "  "
+                       + " backprop " + '%.3f' % self.backpropagation_time + "  "
+                       + "\n")
+            file.close()
+
+    def _expand(self):
+        t0 = time.time()
+        next_action = self.root.selection(self.simulator)
+        t1 = time.time()
+        # next_action.next_state is None means the parent state node of next_action is a terminate node
+        if next_action.next_state is not None:
+            prior, value = self.evaluator(next_action.next_state)
+            next_action.expansion(prior, self.action_num)
+        else:
+            value = 0
+        t2 = time.time()
+        if self.inverse:
+            next_action.backpropagation(-value + 0.)
+        else:
+            next_action.backpropagation(value + 0.)
+        t3 = time.time()
+        return t1 - t0, t2 - t1, t3 - t2
+
+if __name__ == "__main__":
+    pass