The present invention relates to a surface shape inspection method of a large-aperture reflector assembly and belongs to the optical precision measurement technical field. The mirror surface of a reflector in the reflector assembly faces upwards, and an interferometer is adopted to measure the surface shape data W0(m*n) of the reflector in the reflector assembly; the mirror surface of the reflector in the reflector assembly faces downwards, and the interferometer is adopted to measure the surface shape data W0180(i*j) of the reflector in the reflector assembly; surface shape data matrix normalization processing is performed on W0(m*n) and W0180(i*j), so that F0(a*b)=Wa*b+Ka*b and F180(a*b)=Wa*b+G180(a*b)+Ka*b can be obtained; image superposition is performed on normalized surface shape data F0(a*b) and F180(a*b), gravity deformation is eliminated, so that reflector zero-gravity surface shape data F=(F0(a*b)+F180(a*b))/2=Wa*b+Ka*b can be obtained, if the root-mean-square value of the difference value Ka*b of F and Wa*b is not larger than 0.003lambda (lambda=632.8nm), it is considered that the assembling of the reflector assembly meets requirements; and if the root-mean-square value of the difference value Ka*b of F and Wa*b is larger than 0.003lambda, it is considered that the assembling of the reflector assembly does not meet requirements, and the reflector assembly is required to be reassembled.