diff --git a/mmocr/datasets/pipelines/processing.py b/mmocr/datasets/pipelines/processing.py
index 6cfdb165..9a2e1577 100644
--- a/mmocr/datasets/pipelines/processing.py
+++ b/mmocr/datasets/pipelines/processing.py
@@ -170,7 +170,8 @@ class Resize(MMCV_Resize):
                 if polygon is not None:
                     polygons_resize.append(polygon.astype(np.float32))
                 else:
-                    polygons_resize.append(np.zeros_like(polygons[idx]))
+                    polygons_resize.append(
+                        np.zeros_like(polygons[idx], dtype=np.float32))
             results['gt_polygons'] = polygons_resize
 
     def transform(self, results: dict) -> dict:
diff --git a/mmocr/utils/polygon_utils.py b/mmocr/utils/polygon_utils.py
index e661b580..40368525 100644
--- a/mmocr/utils/polygon_utils.py
+++ b/mmocr/utils/polygon_utils.py
@@ -100,8 +100,8 @@ def poly2shapely(polygon: ArrayLike) -> Polygon:
     Returns:
         polygon (Polygon): A polygon object.
     """
-    assert len(polygon) % 2 == 0 and len(polygon) >= 8
     polygon = np.array(polygon, dtype=np.float32)
+    assert polygon.size % 2 == 0 and polygon.size >= 6
 
     polygon = polygon.reshape([-1, 2])
     return Polygon(polygon)
@@ -119,7 +119,8 @@ def polys2shapely(polygons: Sequence[ArrayLike]) -> Sequence[Polygon]:
     return [poly2shapely(polygon) for polygon in polygons]
 
 
-def crop_polygon(polygon: ArrayLike, crop_box: np.ndarray) -> np.ndarray:
+def crop_polygon(polygon: ArrayLike,
+                 crop_box: np.ndarray) -> Union[np.ndarray, None]:
     """Crop polygon to be within a box region.
 
     Args:
@@ -127,19 +128,18 @@ def crop_polygon(polygon: ArrayLike, crop_box: np.ndarray) -> np.ndarray:
         crop_box (ndarray): target box region in shape (4, ).
 
     Returns:
-        np.array or None: Cropped polygon.
+        np.array or None: Cropped polygon. If the polygon is not within the
+            crop box, return None.
     """
-    polygon = np.asarray(polygon, dtype=np.float32)
-    crop_box = np.asarray(crop_box, dtype=np.float32)
-    poly = Polygon(polygon.reshape(-1, 2))
-    crop_poly = Polygon(bbox2poly(crop_box).reshape(-1, 2))
+    poly = poly2shapely(polygon)
+    crop_poly = poly2shapely(bbox2poly(crop_box))
     poly_cropped = poly.intersection(crop_poly)
     if poly_cropped.area == 0.:
         # If polygon is outside crop_box region, return None.
         return None
     else:
-        poly_cropped = np.array(poly_cropped.boundary.xy)[:, :-1]
-        return poly_cropped.reshape(-1)
+        poly_cropped = np.array(poly_cropped.boundary.xy, dtype=np.float32)
+        return poly_cropped[:, :-1].T.reshape(-1)
 
 
 def poly_make_valid(poly: Polygon) -> Polygon:
diff --git a/tests/test_utils/test_polygon_utils.py b/tests/test_utils/test_polygon_utils.py
index 06de7b6e..338ac91d 100644
--- a/tests/test_utils/test_polygon_utils.py
+++ b/tests/test_utils/test_polygon_utils.py
@@ -17,22 +17,25 @@ class TestCropPolygon(unittest.TestCase):
         # polygon cross box
         polygon = np.array([20., -10., 40., 10., 10., 40., -10., 20.])
         crop_box = np.array([0., 0., 60., 60.])
-        target_poly_cropped = np.array([[10., 40., 30., 10., 0., 0., 10.],
-                                        [40., 10., 0., 0., 10., 30., 40.]])
+        target_poly_cropped = np.array(
+            [10, 40, 0, 30, 0, 10, 10, 0, 30, 0, 40, 10])
         poly_cropped = crop_polygon(polygon, crop_box)
-        self.assertTrue(target_poly_cropped.all() == poly_cropped.all())
+        self.assertTrue(
+            poly2shapely(poly_cropped).equals(
+                poly2shapely(target_poly_cropped)))
 
         # polygon inside box
         polygon = np.array([0., 0., 30., 0., 30., 30., 0., 30.]).reshape(-1, 2)
         crop_box = np.array([0., 0., 60., 60.])
         target_poly_cropped = polygon
         poly_cropped = crop_polygon(polygon, crop_box)
-        self.assertTrue(target_poly_cropped.all() == poly_cropped.all())
+        self.assertTrue(
+            poly2shapely(poly_cropped).equals(
+                poly2shapely(target_poly_cropped)))
 
         # polygon outside box
         polygon = np.array([0., 0., 30., 0., 30., 30., 0., 30.]).reshape(-1, 2)
         crop_box = np.array([80., 80., 90., 90.])
-        target_poly_cropped = polygon
         poly_cropped = crop_polygon(polygon, crop_box)
         self.assertEqual(poly_cropped, None)
 
@@ -133,10 +136,10 @@ class TestPolygonUtils(unittest.TestCase):
         self.assertEqual(polys2shapely(polys), polygons)
         # test invalid
         polys = [0, 0, 1]
-        with self.assertRaises(TypeError):
+        with self.assertRaises(AssertionError):
             polys2shapely(polys)
         polys = [0, 0, 1, 0, 1, 1, 0, 1, 1]
-        with self.assertRaises(TypeError):
+        with self.assertRaises(AssertionError):
             polys2shapely(polys)
 
     def test_poly_make_valid(self):