Due to the limitations of configuration scenarios, energy storage capacity configuration takes long time and the net profit value of energy storage capacity is small. Research on energy storage capacity configuration method for power system based on an improved particle swarm optimization (PSO) is proposed. First, the power system energy storage capacity is determined, and the storage capacity configuration constraints are analyzed in respect of the remaining power, charging and discharging efficiency, and reliability of the energy storage system; then, with the objective of maximum net revenue of storage capacity configuration, an economy model of the power system is constructed, and the improved particle swarm algorithm is introduced to solve the model and complete the configuration of the power system energy storage capacity. The experimental results show that the proposed method takes shorter configuration time while owning higher net energy storage capacity revenue, which verifies the application performance of the method.