Abstract: Most existing region-duplication forgery detection algorithms are vulnerable to geometric distortions. Therefore, an effective tampering detection algorithm is proposed for resisting to geometric distortions which involves flipping, rotation, and scaling. Firstly, the circle window images are projected to the rotation and scaling invariance coordinate space by performing log-polar transform. Then circle window radius and frequency band width can be adjusted automatically, which can eliminate redundant image information and noise disturbance, and also increase the phase correlation peak in order to match the circle window images. Finally, the phase correlation can be calculated by adopting automatic adjustment circle window images to obtain the peak position, thus rotation angle and scaling factor can be got. These offsets are applied in region searching, and copied regions and tampered regions can be located. Experimental results show that the proposed method can detect region-duplication forgery image with common geometric distortions, which has high accuracy rate and low false detection rate.