The randomness and intermittent nature of photovoltaic power generation lead to low resource utilization, and energy storage has the characteristics of flexible control and rapid response. It is currently one of the effective means to solve photovoltaic grid connection and improve consumption. At present, the high investment cost of energy storage is the key to restrict its promotion and application. Therefore, the optimal configuration method of energy storage in distributed photovoltaic systems is studied from the perspective of cost. Firstly, take the investment and operating cost of distributed energy storage system as the goal, a two-layer optimization model is established while considering the storage access location, configuration capacity, state of charge, and grid operation status as constraints. And then the optimization model solution method is introduced, that is, the outer layer uses genetic algorithm to optimize energy storage configuration location, power and capacity, and the inner layer uses particle swarm algorithm combined with MATPOWER power flow calculation tool to optimize the daily operation strategy of energy storage. Finally, the IEEE 9-node system is used in Matlab software to verify the feasibility and effectiveness of the proposed optimal configuration method.