diff --git a/ding/model/template/q_learning.py b/ding/model/template/q_learning.py
index 07fa112e0c2f5c92b78ee60e878e12555e09bba7..0bf51c25908f8ffece79c7b53c9424947ded360b 100644
--- a/ding/model/template/q_learning.py
+++ b/ding/model/template/q_learning.py
@@ -1,4 +1,5 @@
 from typing import Union, Optional, Dict, Callable, List
+
 import torch
 import torch.nn as nn
 import treetensor.torch as ttorch
@@ -95,7 +96,7 @@ class DQN(nn.Module):
         """
         x = self.encoder(x)
         x = self.head(x)
-        return ttorch.as_tensor(x)
+        return ttorch.Tensor(x)
 
 
 @MODEL_REGISTRY.register('c51dqn')
diff --git a/ding/policy/dqn.py b/ding/policy/dqn.py
index c3e860f0805ce55d9683e52dca6d5d8cf9869bcc..2dc4618b3d6bb1f1ced0bf2af09b99c5467e79b0 100644
--- a/ding/policy/dqn.py
+++ b/ding/policy/dqn.py
@@ -1,16 +1,15 @@
-from typing import List, Dict, Any, Tuple
-from collections import namedtuple
 import copy
+from collections import namedtuple
+from typing import List, Dict, Any, Tuple
+
 import torch
 import treetensor.torch as ttorch
 
-from ding.torch_utils import Adam, to_device
-from ding.rl_utils import q_nstep_td_data, q_nstep_td_error, get_nstep_return_data, get_train_sample
 from ding.model import model_wrap
+from ding.rl_utils import q_nstep_td_data, q_nstep_td_error, get_nstep_return_data, get_train_sample
+from ding.torch_utils import Adam
 from ding.utils import POLICY_REGISTRY
-from ding.utils.data import default_collate, default_decollate
 from .base_policy import Policy
-from .common_utils import default_preprocess_learn
 
 
 @POLICY_REGISTRY.register('dqn')
@@ -150,7 +149,7 @@ class DQNPolicy(Policy):
         """
         for d in data:
             d['replay_unique_id'] = 0  # TODO
-        data = [ttorch.as_tensor(d) for d in data]
+        data = [ttorch.Tensor(d) for d in data]
         data = ttorch.stack(data)
         data.action.squeeze_(1)
         if self._cfg.learn.ignore_done:
@@ -268,7 +267,7 @@ class DQNPolicy(Policy):
             - necessary: ``logit``, ``action``
         """
         data_id = list(data.keys())
-        data = [ttorch.as_tensor(item) for item in data.values()]
+        data = [ttorch.Tensor(item) for item in data.values()]
         data = ttorch.stack(data)
         if self._cuda:
             data = data.cuda(self._device)
@@ -346,7 +345,7 @@ class DQNPolicy(Policy):
             - necessary: ``action``
         """
         data_id = list(data.keys())
-        data = [ttorch.as_tensor(item) for item in data.values()]
+        data = [ttorch.Tensor(item) for item in data.values()]
         data = ttorch.stack(data)
         if self._cuda:
             data = data.cuda(self._device)
diff --git a/ding/utils/type_helper.py b/ding/utils/type_helper.py
index b959f35201b7df0053a0438132753d3156e9be8f..ae2d9800a0fd3963c91d73e97ab1372b49439ce6 100644
--- a/ding/utils/type_helper.py
+++ b/ding/utils/type_helper.py
@@ -1,7 +1,7 @@
-import typing
-import treetensor
 from collections import namedtuple
-from typing import List, Dict, Tuple, TypeVar, Type
+from typing import List, Dict, Tuple, TypeVar
+
+import treetensor
 
 SequenceType = TypeVar('SequenceType', List, Tuple, namedtuple)
 NestedType = TypeVar('NestedType', Dict, treetensor.torch.Tensor)