Abstract: Subaperture stitching interferometry is an effective means for measuring optical surfaces and systems. But the more subapertures are used, the more serious effect the accumulative error in stitching has on the accuracy. So finding a simple and fast way to remove the accumulative error is the key for improving subaperture stitching. An effective and quick method to eliminate the accumulative error in stitching was proposed in this paper. The plane mirror which was 180 mm 80 mm was tested by six subapertures stitching in the experiment. And the method which was proposed in this paper could get rid of the accumulative error in stitching very well.