Abstract: In order to control the thermal deformation of satellite-borne antenna reflector, a square grille reflector with a diameter of 1200 mm was taken as the research object. Firstly, the finite element modeling strategy for predicting the thermal deformation of the reflector was determined, and the thermal deformation root-mean-square (RMS) of the reflector under three different temperature loads was calculated. On this basis, a new finite element modeling strategy, the equivalent method of laminates, was provided to obtain the equivalent elastic modulus and equivalent thermal expansion coefficient of laminates. Secondly, the grid core was optimized topologically using the square grid reflector as prototype, and compared with the other three geometries, it is found that the square grid reflector is the best structure. Then, the parameters of the square grating reflector were optimized, and the optimal square grating cell size, skin laying mode, square grating laying mode and adhesive layer thickness were found out. Finally, the probability density function distribution of RMS and the contribution rate Pareto diagram of each design parameter were obtained by the confidence analysis of the thermal stability index of the square grating reflector, and the key factors affecting the thermal deformation of the reflector profile were found out.