diff --git a/paddle/math/BaseMatrix.h b/paddle/math/BaseMatrix.h
index dbc217c30f2f2e6d35536d99115282fdb6ed5e06..ea58c861a3d6a03642291c172af76795e90fcb92 100644
--- a/paddle/math/BaseMatrix.h
+++ b/paddle/math/BaseMatrix.h
@@ -458,6 +458,10 @@ public:
   /**
    * @code
    * swap(this, b)
+   * example: swap two Matrices
+   * MatrixPtr cpuA = std::make_shared<CpuMatrix>(height, width);
+   * MatrixPtr cpuB = std::make_shared<CpuMatrix>(height, width);
+   * cpuA->deepSwap(*cpuB);
    * @endcode
    */
   void deepSwap(BaseMatrixT& b);