diff --git a/test/continuous/test_ppo.py b/test/continuous/test_ppo.py
index 8fd5042..a1c9d2b 100644
--- a/test/continuous/test_ppo.py
+++ b/test/continuous/test_ppo.py
@@ -8,6 +8,7 @@ from torch.utils.tensorboard import SummaryWriter
 
 from tianshou.env import VectorEnv
 from tianshou.policy import PPOPolicy
+from tianshou.policy.utils import DiagGaussian
 from tianshou.trainer import onpolicy_trainer
 from tianshou.data import Collector, ReplayBuffer
 
@@ -44,7 +45,7 @@ def get_args():
     parser.add_argument('--max-grad-norm', type=float, default=0.5)
     parser.add_argument('--gae-lambda', type=float, default=0.95)
     parser.add_argument('--rew-norm', type=bool, default=True)
-    parser.add_argument('--dual-clip', type=float, default=5.)
+    # parser.add_argument('--dual-clip', type=float, default=5.)
     parser.add_argument('--value-clip', type=bool, default=True)
     args = parser.parse_known_args()[0]
     return args
@@ -85,7 +86,7 @@ def test_ppo(args=get_args()):
             torch.nn.init.zeros_(m.bias)
     optim = torch.optim.Adam(list(
         actor.parameters()) + list(critic.parameters()), lr=args.lr)
-    dist = torch.distributions.Normal
+    dist = DiagGaussian
     policy = PPOPolicy(
         actor, critic, optim, dist, args.gamma,
         max_grad_norm=args.max_grad_norm,
@@ -93,7 +94,8 @@ def test_ppo(args=get_args()):
         vf_coef=args.vf_coef,
         ent_coef=args.ent_coef,
         reward_normalization=args.rew_norm,
-        dual_clip=args.dual_clip,
+        # dual_clip=args.dual_clip,
+        # dual clip cause monotonically increasing log_std :)
         value_clip=args.value_clip,
         # action_range=[env.action_space.low[0], env.action_space.high[0]],)
         # if clip the action, ppo would not converge :)
diff --git a/tianshou/policy/modelfree/ppo.py b/tianshou/policy/modelfree/ppo.py
index 85cb7e1..3f9b5e9 100644
--- a/tianshou/policy/modelfree/ppo.py
+++ b/tianshou/policy/modelfree/ppo.py
@@ -53,7 +53,7 @@ class PPOPolicy(PGPolicy):
                  ent_coef: float = .01,
                  action_range: Optional[Tuple[float, float]] = None,
                  gae_lambda: float = 0.95,
-                 dual_clip: float = 5.,
+                 dual_clip: float = None,
                  value_clip: bool = True,
                  reward_normalization: bool = True,
                  **kwargs) -> None:
diff --git a/tianshou/policy/modelfree/sac.py b/tianshou/policy/modelfree/sac.py
index d1357a5..6e1a8f5 100644
--- a/tianshou/policy/modelfree/sac.py
+++ b/tianshou/policy/modelfree/sac.py
@@ -6,6 +6,7 @@ from typing import Dict, Tuple, Union, Optional
 
 from tianshou.data import Batch
 from tianshou.policy import DDPGPolicy
+from tianshou.policy.utils import DiagGaussian
 
 
 class SACPolicy(DDPGPolicy):
@@ -94,13 +95,12 @@ class SACPolicy(DDPGPolicy):
         obs = getattr(batch, input)
         logits, h = self.actor(obs, state=state, info=batch.info)
         assert isinstance(logits, tuple)
-        dist = torch.distributions.Normal(*logits)
+        dist = DiagGaussian(*logits)
         x = dist.rsample()
         y = torch.tanh(x)
         act = y * self._action_scale + self._action_bias
         log_prob = dist.log_prob(x) - torch.log(
             self._action_scale * (1 - y.pow(2)) + self.__eps)
-        log_prob = torch.unsqueeze(torch.sum(log_prob, 1), 1)
         act = act.clamp(self._range[0], self._range[1])
         return Batch(
             logits=logits, act=act, state=h, dist=dist, log_prob=log_prob)
diff --git a/tianshou/policy/utils.py b/tianshou/policy/utils.py
new file mode 100644
index 0000000..56aa035
--- /dev/null
+++ b/tianshou/policy/utils.py
@@ -0,0 +1,13 @@
+import torch
+
+
+class DiagGaussian(torch.distributions.Normal):
+    """Diagonal Gaussian Distribution
+
+    """
+
+    def log_prob(self, actions):
+        return super().log_prob(actions).sum(-1, keepdim=True)
+
+    def entropy(self):
+        return super().entropy().sum(-1)