diff --git a/mmdet/models/layers/ema.py b/mmdet/models/layers/ema.py
index bce503c4641..73a0ca67c28 100644
--- a/mmdet/models/layers/ema.py
+++ b/mmdet/models/layers/ema.py
@@ -63,4 +63,4 @@ def avg_func(self, averaged_param: Tensor, source_param: Tensor,
         """
         momentum = (1 - self.momentum) * math.exp(
             -float(1 + steps) / self.gamma) + self.momentum
-        averaged_param.mul_(1 - momentum).add_(source_param, alpha=momentum)
+        averaged_param.lerp_(source_param, momentum)