diff --git a/colossalai/amp/naive_amp/grad_scaler/dynamic_grad_scaler.py b/colossalai/amp/naive_amp/grad_scaler/dynamic_grad_scaler.py
index 1ac26ee91..6d6f2f287 100644
--- a/colossalai/amp/naive_amp/grad_scaler/dynamic_grad_scaler.py
+++ b/colossalai/amp/naive_amp/grad_scaler/dynamic_grad_scaler.py
@@ -1,10 +1,12 @@
 #!/usr/bin/env python
 # -*- encoding: utf-8 -*-
 
-import torch
-from .base_grad_scaler import BaseGradScaler
 from typing import Optional
 
+import torch
+
+from .base_grad_scaler import BaseGradScaler
+
 __all__ = ['DynamicGradScaler']