The problem of power abandonment and fluctuation with a high proportion of renewable energy connected to the grid can be solved by configuring energy storage. However, the cost of energy storage currently is high and it is difficult to promote and apply on a large scale. In addition, existing research focuses on planning for energy storage. The optimal capacity of energy storage in a single season ignores the impact of seasonal fluctuation in wind power and photovoltaic output on the scale of energy storage. In order to solve the above problems, an optimal allocation method for energy storage considering seasonal fluctuation of renewable energy output and load demand is proposed. The investment and operation cost of energy storage is calculated by the equivalent number of cycles. And the expected continuous discharge time is used to deal with the correlation of capacity and power. The capacity and power of energy storage are configured from the perspective of the full life cycle benefits of energy storage and the comprehensive utilization rate of wind and photovoltaic. The simulation results show that, compared with the pursuit of maximizing energy storage revenue or using a single typical day for energy storage configuration, the method proposed can not only ensure the economy of energy storage, but also further improve the utilization rate of renewable energy.