The splicing measuring method applied in large-aperture aspheric surface optical elements, can extend the range of precision measuring instrument and expand measurement capability of the system. In this paper, two methods are proposed: the fitting evaluation method and the curvature comparison method in the light of how to reject the redundant data of the splicing coincidence part, and the theoretical analysis are investigated to calculate the theoretical error. The Talysurf PGI 1240 profilometer of Taylor Hobson Company is used as application object to do experimental research. The results show that the curvature comparison method is feasible and has characteristic such as fast speed, high precision, and good operability.