Abstract: Optimal allocation of energy storage system capacity is one of the effective measures to improve system stability and reduce the cost of micro-grid. In this paper, an energy management strategy considering the state of charge（SOC） is proposed to configure the capacity of hybrid energy storage system（HESS）. The stability and economic benefits of micro-grid operation are analyzed, and a PV micro-grid energy storage model with super-capacitor and storage battery is established with the aim of minimizing the sum of the life cycle cost and the electricity cost. Combining PV available energy and load demand power, the improved energy management strategy and particle swarm optimization algorithm are used to establish a two-layer optimization model for PV micro-grid HESS capacity allocation. Taking the actual data of a certain place as an example, the optimization problem is solved. The optimization results are compared with the traditional HESS method, and the effectiveness of the proposed method is verified, which provides a reference for HESS capacity optimization of PV micro-grid.