Due to the limitation of the satellite platform, the bandwidth and power resources of the satellite transponder are limited, and the improvement of resource utilization is particularly important. Aiming at the problem of joint power and bandwidth allocation in multi-beam satellite communication system, this paper proposes a joint bandwidth and power allocation scheme based on improved particle swarm optimization algorithm. The scheme aims to minimize the total second-order service rejection of the system. The optimal solution is obtained by introducing an improved particle swarm optimization algorithm with inertia weight, local suppression mechanism and penalty function. Finally, a balance between the total capacity of the system and the fairness of the user′s access capacity is achieved.The simulation results show that compared with the traditional algorithm, the method based on the improved particle swarm optimization algorithm proposed in this paper can significantly improve the effect of joint bandwidth and power allocation of multi-beam satellite communication system.