diff --git a/doc/api/v2/fluid.rst b/doc/api/v2/fluid.rst
index 43fc19dc492bbc119f2356034b81c65e443db2fa..5f15cad2b530dfb3702357b3c26885ac2a7b7beb 100644
--- a/doc/api/v2/fluid.rst
+++ b/doc/api/v2/fluid.rst
@@ -15,4 +15,4 @@ Fluid
     fluid/param_attr.rst
     fluid/profiler.rst
     fluid/regularizer.rst
-
+    fluid/io.rst
diff --git a/doc/api/v2/fluid/io.rst b/doc/api/v2/fluid/io.rst
new file mode 100644
index 0000000000000000000000000000000000000000..67f68c4e9e16b379207b8de114cdf769e056f78e
--- /dev/null
+++ b/doc/api/v2/fluid/io.rst
@@ -0,0 +1,10 @@
+===========
+IO
+===========
+
+
+
+is_parameter
+-----------
+..  autofunction:: paddle.v2.fluid.io.is_parameter
+    :noindex:
diff --git a/python/paddle/v2/fluid/io.py b/python/paddle/v2/fluid/io.py
index c63567601accd8c072368351f2838857bb61c818..eef1e283c2c9db6de375b70f94c50f8dce140d52 100644
--- a/python/paddle/v2/fluid/io.py
+++ b/python/paddle/v2/fluid/io.py
@@ -11,6 +11,16 @@ __all__ = [
 
 
 def is_parameter(var):
+    """Check whether the variable is a Parameter.
+
+    This function checks whether the input variable is a Parameter.
+
+    Args:
+        var : The input variable.
+
+    Returns:
+        boolean result whether the variable is a Parameter.
+    """
     return isinstance(var, Parameter)