diff --git a/python/paddle/fluid/tests/unittests/test_diag.py b/python/paddle/fluid/tests/unittests/test_diag.py
index b270d47316f40..0e645e5fb7d65 100644
--- a/python/paddle/fluid/tests/unittests/test_diag.py
+++ b/python/paddle/fluid/tests/unittests/test_diag.py
@@ -18,6 +18,7 @@
 from op_test import OpTest
 
 import paddle
+import paddle.fluid.core as core
 from paddle.fluid import Program, program_guard
 
 
@@ -42,14 +43,26 @@ def init_config(self):
         self.case = np.array([3], dtype='int32')
 
 
+class TestDiagOpFp16(unittest.TestCase):
+    def test_fp16(self):
+        x_np = np.array([3], dtype='float16')
+        with paddle.static.program_guard(paddle.static.Program()):
+            x = paddle.static.data(shape=[1, 0], name='x', dtype='float16')
+            out = paddle.diag(x)
+            if core.is_compiled_with_cuda():
+                place = paddle.CUDAPlace(0)
+                exe = paddle.static.Executor(place)
+                exe.run(paddle.static.default_startup_program())
+                out = exe.run(feed={'x': x_np}, fetch_list=[out])
+
+
 class TestDiagError(unittest.TestCase):
     def test_errors(self):
         paddle.enable_static()
         with program_guard(Program(), Program()):
 
             def test_diag_type():
-                x = [1, 2, 3]
-                output = paddle.diag(x=x)
+                return paddle.diag(x=[1, 2, 3])
 
             self.assertRaises(TypeError, test_diag_type)
 
diff --git a/python/paddle/tensor/creation.py b/python/paddle/tensor/creation.py
index 83379ff69c8a4..67e63d5c29434 100644
--- a/python/paddle/tensor/creation.py
+++ b/python/paddle/tensor/creation.py
@@ -1627,7 +1627,7 @@ def diag(x, offset=0, padding_value=0, name=None):
     If ``offset`` < 0, it is subdiagonal.
 
     Args:
-        x (Tensor): The input tensor. Its shape is either 1-D or 2-D. Its data type should be float32, float64, int32, int64.
+        x (Tensor): The input tensor. Its shape is either 1-D or 2-D. Its data type should be float16, float32, float64, int32, int64.
         offset (int, optional): The diagonal offset. A positive value represents superdiagonal, 0 represents the main diagonal, and a negative value represents subdiagonal.
         padding_value (int|float, optional): Use this value to fill the area outside the specified diagonal band. Only takes effect when the input is a 1-D Tensor. The default value is 0.
         name (str, optional): For details, please refer to :ref:`api_guide_Name`. Generally, no setting is required. Default: None.
@@ -1694,7 +1694,7 @@ def diag(x, offset=0, padding_value=0, name=None):
         check_dtype(
             x.dtype,
             'x',
-            ['float32', 'float64', 'int32', 'int64'],
+            ['float16', 'float32', 'float64', 'int32', 'int64'],
             'diag_v2',
         )
         check_type(offset, 'offset', (int), 'diag_v2')