diff --git a/paddle/function/BufferArg.h b/paddle/function/BufferArg.h
index 12352ba29e33920ba65bd66088b6f7cc53517b52..28542a86574812048ff5f72a2d4b2c188f7e30bf 100644
--- a/paddle/function/BufferArg.h
+++ b/paddle/function/BufferArg.h
@@ -39,7 +39,6 @@ enum SparseDataFormat { SPARSE_CSR_FORMAT = 0, SPARSE_CSC_FORMAT = 1 };
 class BufferArg;
 class SequenceArg;
 class SparseMatrixArg;
-typedef std::shared_ptr<BufferArg> BufferArgPtr;
 
 /**
  * \brief BufferArg used as the argument type of Function.
@@ -50,6 +49,11 @@ typedef std::shared_ptr<BufferArg> BufferArgPtr;
  * 3. SequenceArg for a Buffer of sequence data.
  * 4. SparseMatrixArg for a Buffer of sparse matrix.
  *
+ * Buffer shape
+ * For most buffers, the first dimension `shape()[0]` represents
+ * the size of the mini-batch.
+ *
+ * Buffer argType
  * There is an ArgType property for the BufferArg used as Function Output.
  * Whether the result of the Function calculation is assigned to the
  * output Buffer or added to the output Buffer is determined by the
@@ -71,6 +75,14 @@ public:
   ArgType getArgType() const { return argType_; }
 
 public:
+  BufferArg(ValueType valueType,
+            const TensorShape& shape,
+            ArgType argType = UNSPECIFIED)
+      : buf_(nullptr),
+        valueType_(valueType),
+        shape_(shape),
+        argType_(argType) {}
+
   BufferArg(void* buf,
             ValueType valueType,
             const TensorShape& shape,
@@ -170,6 +182,12 @@ protected:
 // if a < b then value_.buf_[a] < value_.buf_[b]
 class SequenceIdArg : public BufferArg {
 public:
+  SequenceIdArg(const TensorShape& shape, ArgType argType = UNSPECIFIED)
+      : BufferArg(VALUE_TYPE_INT32, shape, argType) {
+    CHECK_EQ(shape_.ndims(), (size_t)1);
+    numSeqs_ = shape_[0] - 1;
+  }
+
   SequenceIdArg(void* buf,
                 const TensorShape& shape,
                 ArgType argType = UNSPECIFIED)
@@ -190,9 +208,18 @@ private:
   size_t numSeqs_;
 };
 
-// sequence data
+// sequences data
+// For mini-batch calculate,
+// one batch can contain more than one sequence of data.
+// SequenceArg can be used to represent sequences that contain multiple
+// unequal lengths.
 class SequenceArg : public BufferArg {
 public:
+  SequenceArg(ValueType valueType,
+              const TensorShape& shape,
+              ArgType argType = UNSPECIFIED)
+      : BufferArg(valueType, shape, argType), startPositions_(TensorShape()) {}
+
   SequenceArg(void* buf,
               ValueType valueType,
               const TensorShape& shape,
@@ -210,6 +237,8 @@ public:
 
   void* getIdBuf() const { return startPositions_.data(); }
   size_t numSeqs() const { return startPositions_.numSeqs(); }
+  SequenceIdArg& getSequenceId() { return startPositions_; }
+  const SequenceIdArg& getSequenceId() const { return startPositions_; }
 
 private:
   SequenceIdArg startPositions_;
diff --git a/paddle/function/FunctionTest.cpp b/paddle/function/FunctionTest.cpp
index eb05ca9a2190d56b925fc063778459315d312d4e..03c609b524277763b73c2e100d9d9c5081c7d3f6 100644
--- a/paddle/function/FunctionTest.cpp
+++ b/paddle/function/FunctionTest.cpp
@@ -84,6 +84,10 @@ void testBufferArgs(const BufferArgs& inputs,
   }
 }
 
+void testBufferArgs(const BufferArgs& inputs, const CheckBufferArg& check) {
+  check(inputs[0]);
+}
+
 TEST(Arguments, Matrix) {
   MatrixPtr matrix = Matrix::create(100, 200);
   CheckBufferArg check = [=](const BufferArg& arg) {
@@ -144,4 +148,18 @@ TEST(Arguments, CpuSparseMatrix) {
   testBufferArgs(argments, checkFunc);
 }
 
+TEST(Arguments, BufferArg) {
+  BufferArg arg(nullptr, VALUE_TYPE_FLOAT, {1, 2, 3});
+  CheckBufferArg check = [=](const BufferArg& arg) {
+    EXPECT_EQ(arg.shape().ndims(), 3);
+    EXPECT_EQ(arg.shape()[0], 1);
+    EXPECT_EQ(arg.shape()[1], 2);
+    EXPECT_EQ(arg.shape()[2], 3);
+  };
+
+  BufferArgs argments;
+  argments.addArg(arg);
+  testBufferArgs(argments, check);
+}
+
 }  // namespace paddle