Method for detecting wavefront aberration for optical imaging system based on grating shearing interferometer, the grating shearing interferometer system comprising a light source and illumination system, an optical imaging system to be tested, a one-dimensional diffraction grating plate, a two-dimensional diffraction grating plate, a two-dimensional photoelectric sensor, and a computing unit. The one-dimensional and two-dimensional diffraction grating plates are respectively placed on the object plane and the image plane of the optical imaging system to be tested. By collecting interferograms with phase-shifting amounts of 0, π/2, π, 3π/2 and N sets of α, π-α, 2π-α (where, N = 2 ⁢ ( fix ⁡ ( ceil ⁡ ( 1 ⁢ / ⁢ s ) 2 ) + 1 ) , s is the shear ratio of the grating shearing interferometer system), combined with a certain phase retrieval algorithm, the influence of all high-order diffraction beams on the phase retrieval accuracy is eliminated, and finally the detection accuracy of wavefront aberration for the imaging system to be tested is improved.