diff --git a/python/paddle/v2/fluid/layers/nn.py b/python/paddle/v2/fluid/layers/nn.py
index 2adce99d052639ec7d9063b1c234c623e7cdb9c6..941675ec3e1705896c83fb4f61d3f5aa7afb844e 100644
--- a/python/paddle/v2/fluid/layers/nn.py
+++ b/python/paddle/v2/fluid/layers/nn.py
@@ -163,8 +163,9 @@ def embedding(input, size, is_sparse=False, param_attr=None, dtype='float32'):
     Examples:
         .. code-block:: python
 
+          dict_size = len(dataset.ids)
           data = fluid.layers.data(name='ids', shape=[32, 32], dtype='float32')
-          fc = fluid.layers.embedding(input=data, size=16)
+          fc = fluid.layers.embedding(input=data, size=[dict_size, 16])
     """
 
     helper = LayerHelper('embedding', **locals())