A method for high-accuracy wavefront measurement based on grating shearing interferometry, which adopts a grating shearing interferometer system comprising an illuminating system, an optical imaging system under test, an object plane diffraction grating plate, an image plane diffraction grating plate, a two-dimensional photoelectric sensor, and a calculation processing unit. The object plane diffraction grating plate and the image plane diffraction grating plate are respectively arranged on the object plane and the image plane of the optical imaging system under test. The shearing phase of 1st-order diffracted beam and −1st-order diffracted beam is exactly extracted through phase shifting method, and the original wavefront is obtained by carrying out reconstruction algorithm according to a shear ratio of 2s, such that the accuracy of wavefront measurement of the optical imaging system under test is improved, wherein s is the shear ratio of the grating shearing interferometer.