diff --git a/mmcv/ops/deform_conv.py b/mmcv/ops/deform_conv.py
index 2c31a6efb6..5c45bd4ebb 100644
--- a/mmcv/ops/deform_conv.py
+++ b/mmcv/ops/deform_conv.py
@@ -200,7 +200,7 @@ class DeformConv2d(nn.Module):
             channels to output channels. Default: 1.
         deform_groups (int): Number of deformable group partitions.
         bias (bool): If True, adds a learnable bias to the output.
-            Default: True.
+            Default: False.
 
     """
 
@@ -234,7 +234,6 @@ def __init__(self,
         self.dilation = _pair(dilation)
         self.groups = groups
         self.deform_groups = deform_groups
-        self.bias = bias
         # enable compatibility with nn.Conv2d
         self.transposed = False
         self.output_padding = _single(0)
@@ -301,7 +300,8 @@ def __repr__(self):
         s += f'dilation={self.dilation},\n'
         s += f'groups={self.groups},\n'
         s += f'deform_groups={self.deform_groups},\n'
-        s += f'bias={self.bias})'
+        # bias is not supported in DeformConv2d.
+        s += 'deform_groups=False)'
         return s
 
 
diff --git a/tests/test_ops/test_deform_conv.py b/tests/test_ops/test_deform_conv.py
index 58b2e9f631..b99df8d011 100644
--- a/tests/test_ops/test_deform_conv.py
+++ b/tests/test_ops/test_deform_conv.py
@@ -1,4 +1,5 @@
 import numpy as np
+import pytest
 import torch
 
 input = [[[[1., 2., 3.], [0., 1., 2.], [3., 5., 2.]]]]
@@ -56,6 +57,20 @@ def _test_deformconv(self, dtype=torch.float, threshold=1e-3):
         assert np.allclose(model.weight.grad.detach().cpu().numpy(),
                            gt_deform_weight_grad, threshold)
 
+        from mmcv.ops import DeformConv2d
+        # test bias
+        model = DeformConv2d(1, 1, 2, stride=1, padding=0)
+        assert not hasattr(model, 'bias')
+        # test bias=True
+        with pytest.raises(AssertionError):
+            model = DeformConv2d(1, 1, 2, stride=1, padding=0, bias=True)
+        # test in_channels % group != 0
+        with pytest.raises(AssertionError):
+            model = DeformConv2d(3, 2, 3, groups=2)
+        # test out_channels % group != 0
+        with pytest.raises(AssertionError):
+            model = DeformConv2d(3, 4, 3, groups=3)
+
     def test_deformconv(self):
         self._test_deformconv(torch.double)
         self._test_deformconv(torch.float)