In this paper, a dynamic capacity planning model of photovoltaic storage system is proposed considering the operation characteristics of conventional units. With the bi-layer model method, the upper level planning takes the total cost of photovoltaic storage system and conventional power grid units as the objective, and obtains the capacity configuration scheme of photovoltaic storage system through gray wolf algorithm; the lower level optimization takes the minimum daily operation cost of photovoltaic storage system as the objective, and calls the branch and bound algorithm of CPLEX to solve the problem through MATLAB, and obtains the conventional units of photovoltaic, battery and power grid Scheduling scheme. Finally, the rationality of the model is verified by an example. The simulation results show that this method can obtain the optimal energy allocation scheme of optical storage system, and take into account the energy consumption of conventional units in power grid, so as to reduce the power generation cost and improve the environmental benefits.