Abstract: In order to study the effects of 1070nm continuous wave laser irradiation on output performance of three-junction GaAs solar cell, a physical model was established by software COMSOL. The influence of laser power density, spot radius, anti reflection film, thermal radiation and thermal convection on temperature field were studied by numerical simulation. The results show that, absorption coefficient, thermal conductivity and photoelectric conversion efficiency are three main factors of temperature evolution. The magnitude of temperature increases with the increasing of laser power density. The smaller the spot radius is, the greater the temperature difference of cell surface. The conversion efficiency of solar cells can be effectively improved by anti reflection film structure, but it also makes battery temperature higher. Thermal convection dominates under the lower temperature (300K~400K) of the battery. When the incident power density is 16.7W/cm² and spot radius is the same as the cell radius, after 20s, the central temperature of battery can reach 501.521K and lead to photoelectric conversion efficiency of 0. The numerical simulation results are in good agreement with the experimental results. The study provides a theoretical basis for the research of the mechanism of laser damage solar cells.