In order to realize sub-aperture stitching measurement of large optical wavfront, sub-aperture location compensation algorithm is introduced and the ability to compensate the mechanical location error is analyzed. Based on the aperture of the tested optical system and the sub-aperture, the layout of the sub-aperture is calculated. In the range of the mechanical location error, stitching the sub-aperture to get the location compensation coefficients and the adjusting error coefficients, the full aperture of the tested wavefront is got and the large optical wavefront is tested. The feasiblility of the algorithm is tested by the simulation, and the wavefront of the optical system with aperture of 200 nm is tested when the mechanical translation precision is 1 mm and rotation precision is 0.5°. The result indicates the stability of the algorithm and can effectively compensate the sub-aperturre location error caused by the mechanical, which can reduce the high requirement of the mechanical platform.