Abstract: In order to solve the problem of fluctuation absorption and economic operation of power system with high proportion of renewable energy access, the capacity allocation optimization of hybrid photovoltaic energy storage system based on improved CSO algorithm is studied. By constructing a hybrid energy storage system model including battery and supercapacitor, an optimization function with the minimum life cycle cost and comprehensive consideration of operation constraints is established. An improved CSO algorithm combining horizontal and vertical cross search mechanism is designed to realize collaborative optimization of energy storage power and capacity. Through the comparative analysis before and after optimization, it is proved that the proposed method can effectively improve the economy, stability and renewable energy consumption capacity of the system, and provide theoretical basis and decision support for the planning and operation of the integrated wind, solar and storage system.