In order to enhance the available probably ratio and to improve the temperature level and difference in a specific geostationary earth orbit (GEO) laser communication system, the structure of baffle was optimized. The baffle was uniformly installed grids on internal surface on the basis of GEO orbit external thermal flux characteristics, without the decrease of laser communication signal property. Firstly, the impact of grid and baffle inner wall on the solar view factor of the primary mirror was discussed in terms of energy shield ratio standard less than 5%. Then, the thermal simulation of temperature level and difference on the primary and secondary mirrors were performed by IDEAS, in which the influence of number and layout of grids on temperature indexes was analyzed. Finally, the laser communication available probably ratio with the optimized baffle was calculated. The results show that deploying 4 equally distributed grids along both parallel and vertical directions to the equator in the baffle, the available communication probably ratio is raised from 81.51% to 91.21% in comparison with the one of traditional cylindrical hollow baffle.