diff --git a/python/paddle/fluid/layers/nn.py b/python/paddle/fluid/layers/nn.py
index 7757226898144e33a6a18467eead2b91ed9256a9..170bad1aa3b6db2b84a1d07b2b2d7e1cbbb1930e 100644
--- a/python/paddle/fluid/layers/nn.py
+++ b/python/paddle/fluid/layers/nn.py
@@ -6690,7 +6690,6 @@ def clip_by_norm(x, max_norm, name=None):
         out = helper.create_variable(
             name=name, dtype=x.dtype, persistable=False)
 
-    # max_norm should always be set
     helper.append_op(
         type="clip_by_norm",
         inputs={"X": x},