diff --git a/python/paddle/fluid/initializer.py b/python/paddle/fluid/initializer.py
index 01b140b92e7e531d7edbb84c7bc92c7631c9c06c..b14234b59984b051b6cd0c98da8a0c1ff7d32655 100644
--- a/python/paddle/fluid/initializer.py
+++ b/python/paddle/fluid/initializer.py
@@ -744,6 +744,7 @@ class BilinearInitializer(Initializer):
         .. code-block:: python
 
             import paddle.fluid as fluid
+            import math
             factor = 2
             C = 2
             B = 8