diff --git a/python/paddle/v2/fluid/layers/nn.py b/python/paddle/v2/fluid/layers/nn.py
index a5bbf4f2bf6bcc377dd833713e1e12f6a54ed81b..d21d9e4d53edd4a81c04b7048b207d8a0e01a3e3 100644
--- a/python/paddle/v2/fluid/layers/nn.py
+++ b/python/paddle/v2/fluid/layers/nn.py
@@ -41,7 +41,7 @@ def fc(input,
 
     .. math::
 
-        Out = Act\left({\sum_{i=0}^{N-1}W_iX_i + b}\right)
+        Out = Act({\sum_{i=0}^{N-1}W_iX_i + b})
 
     In the above equation: