The rotation absolute algorithm is stuided for the grating lateral-shearing interferometer, and the first 36-term Zernike polynomials are used to characterize the asymmetric term in the systemic errors of the shearing setup. The research results show that the relatively ideal measurement precision can be obtained after the systemic errors are removed if the absolute algorithm of surface figure testing is used to the testing of wavefront aberration in lens system. In addition, the RMS of the repeatability of the experimental data can approach 0.14 nm.