A reflector is the core element of optical instruments, and the precision measurement of its shape has always been an important part of research areas. A method for rapid shape measurement based on the deformation of two-dimensional optical lattice is proposed based on the variable spatial periodic distribution optical lattice generated by the modulation of optical fields. Based on the theory of geometric optics and space three-dimensional transformation, a mathematic correlation model between a two-dimensional optical lattice deformation and a three-dimensional shape of reflector is established. A surface reconstruction algorithm based on lattice centroid is proposed. The measurement range and single pixel resolution of the proposed measurement method are analyzed. The multi-dip angle experiments are carried out, and a submicron measurement of the reflector with a diameter of 10.5 mm is achieved. The feasibility of the method is verified when we compare the test data with the measurement data of the commercial interferometer. In addition, the method has the characteristics of high precision, fast speed and strong adaptability.