diff --git a/python/paddle/fluid/layers/nn.py b/python/paddle/fluid/layers/nn.py
index b34b0848e8..7a9500a2df 100644
--- a/python/paddle/fluid/layers/nn.py
+++ b/python/paddle/fluid/layers/nn.py
@@ -1316,7 +1316,7 @@ def dropout(x,
                                         1. downgrade_in_infer(default), downgrade the outcome at inference
 
                                            - train: out = input * mask
-                                           - inference: out = input * (1 - dropout_prob)
+                                           - inference: out = input * (1.0 - dropout_prob)
 
                                            (mask is a tensor same shape with input, value is 0 or 1
                                            ratio of 0 is dropout_prob)