In recent years, the development of satellite communication is rapid, but the security problems become more significant. In this paper, from the perspective of improving the physical layer security, in the context of secure multicast transmission, we apply the sparse array directional modulation technology to improve the physical layer security. However, the inherent problem of sparse array is the existence of high sidelobe, which threatens the security of information transmission. Simulated annealing algorithm is used to optimize the selection of antenna subset, and some antenna combinations with high sidelobe are removed to obtain the optimized antenna subset codebook. When the distance between each ideal receiver and transmitter is different, the weighted simulated annealing algorithm method is introduced to allocate different transmission power to each receiver with different distance to improve the reception quality of each receiver. Finally, the simulation results verify the correctness of the above theory.