diff --git a/tianshou/core/policy/base.py b/tianshou/core/policy/base.py
index eecfc4f..025abd5 100644
--- a/tianshou/core/policy/base.py
+++ b/tianshou/core/policy/base.py
@@ -15,7 +15,7 @@ __all__ = [
     'QValuePolicy',
 ]
 
-# TODO: separate actor and critic, we should focus on it once we finish the basic module.
+# TODO: a even more "base" class for policy
 
 
 class QValuePolicy(object):
diff --git a/tianshou/core/policy/dqn.py b/tianshou/core/policy/dqn.py
index 39f6a16..d03dbd4 100644
--- a/tianshou/core/policy/dqn.py
+++ b/tianshou/core/policy/dqn.py
@@ -1,5 +1,16 @@
 from tianshou.core.policy.base import QValuePolicy
 import tensorflow as tf
+import sys
+sys.path.append('..')
+import value_function.action_value as value_func
+
+
+class DQN_refactor(object):
+    """
+    use DQN from value_function as a member
+    """
+    def __init__(self, value_tensor, observation_placeholder, action_placeholder):
+        self._network = value_func.DQN(value_tensor, observation_placeholder, action_placeholder)
 
 
 class DQN(QValuePolicy):
diff --git a/tianshou/core/value_function/__init__.py b/tianshou/core/value_function/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tianshou/core/value_function/action_value.py b/tianshou/core/value_function/action_value.py
new file mode 100644
index 0000000..cb8acc8
--- /dev/null
+++ b/tianshou/core/value_function/action_value.py
@@ -0,0 +1,53 @@
+from base import ValueFunctionBase
+import tensorflow as tf
+
+
+class ActionValue(ValueFunctionBase):
+    """
+    class of action values Q(s, a).
+    """
+    def __init__(self, value_tensor, observation_placeholder, action_placeholder):
+        self._action_placeholder = action_placeholder
+        super(ActionValue, self).__init__(
+            value_tensor=value_tensor,
+            observation_placeholder=observation_placeholder
+        )
+
+    def get_value(self, observation, action):
+        """
+
+        :param observation: numpy array of observations, of shape (batchsize, observation_dim).
+        :param action: numpy array of actions, of shape (batchsize, action_dim)
+        # TODO: Atari discrete action should have dim 1. Super Mario may should have, say, dim 5, where each can be 0/1
+        :return: numpy array of state values, of shape (batchsize, )
+        # TODO: dealing with the last dim of 1 in V(s) and Q(s, a)
+        """
+        sess = tf.get_default_session()
+        return sess.run(self.get_value_tensor(), feed_dict=
+        {self._observation_placeholder: observation, self._action_placeholder:action})[:, 0]
+
+
+class DQN(ActionValue):
+    """
+    class of the very DQN architecture. Instead of feeding s and a to the network to get a value, DQN feed s to the
+    network and the last layer is Q(s, *) for all actions
+    """
+    def __init__(self, value_tensor, observation_placeholder, action_placeholder):
+        """
+        :param value_tensor: of shape (batchsize, num_actions)
+        :param observation_placeholder: of shape (batchsize, observation_dim)
+        :param action_placeholder: of shape (batchsize, )
+        """
+        self._value_tensor_all_actions = value_tensor
+        canonical_value_tensor = value_tensor[action_placeholder]  # maybe a tf.map_fn. for now it's wrong
+
+        super(DQN, self).__init__(value_tensor=canonical_value_tensor,
+                                  observation_placeholder=observation_placeholder,
+                                  action_placeholder=action_placeholder)
+
+    def get_value_all_actions(self, observation):
+        sess = tf.get_default_session()
+        return sess.run(self._value_tensor_all_actions, feed_dict={self._observation_placeholder: observation})
+
+    def get_value_tensor_all_actions(self):
+        return self._value_tensor_all_actions
\ No newline at end of file
diff --git a/tianshou/core/value_function/base.py b/tianshou/core/value_function/base.py
new file mode 100644
index 0000000..0b27759
--- /dev/null
+++ b/tianshou/core/value_function/base.py
@@ -0,0 +1,23 @@
+
+# TODO: linear feature baseline also in tf?
+class ValueFunctionBase(object):
+    """
+    base class of value functions. Children include state values V(s) and action values Q(s, a)
+    """
+    def __init__(self, value_tensor, observation_placeholder):
+        self._observation_placeholder = observation_placeholder
+        self._value_tensor = value_tensor
+
+    def get_value(self, **kwargs):
+        """
+
+        :return: batch of corresponding values in numpy array
+        """
+        raise NotImplementedError()
+
+    def get_value_tensor(self):
+        """
+
+        :return: tensor of the corresponding values
+        """
+        return self._value_tensor
diff --git a/tianshou/core/value_function/state_value.py b/tianshou/core/value_function/state_value.py
new file mode 100644
index 0000000..04fe442
--- /dev/null
+++ b/tianshou/core/value_function/state_value.py
@@ -0,0 +1,23 @@
+from base import ValueFunctionBase
+import tensorflow as tf
+
+
+class StateValue(ValueFunctionBase):
+    """
+    class of state values V(s).
+    """
+    def __init__(self, value_tensor, observation_placeholder):
+        super(StateValue, self).__init__(
+            value_tensor=value_tensor,
+            observation_placeholder=observation_placeholder
+        )
+
+    def get_value(self, observation):
+        """
+
+        :param observation: numpy array of observations, of shape (batchsize, observation_dim).
+        :return: numpy array of state values, of shape (batchsize, )
+        # TODO: dealing with the last dim of 1 in V(s) and Q(s, a)
+        """
+        sess = tf.get_default_session()
+        return sess.run(self.get_value_tensor(), feed_dict={self._observation_placeholder: observation})[:, 0]
\ No newline at end of file