Abstract: In order to solve the fluctuation and uncertainty of wind power output, an optimal allocation method of battery storage capacity for wind farms based on battery storage grouping control strategy and its operational imbalance is proposed. Firstly, based on the comparative analysis of different battery storage grouping strategies, a three-cell grouping control strategy and charging/discharging operation mode of the combined wind storage system are proposed, and a multi-objective battery storage capacity allocation optimization model is constructed taking into account the economic cost, decay index and lifetime. Then, the wind power data are processed by the variational modal decomposition method, and the optimal battery storage capacity allocation scheme is obtained by the joint solution of the non-dominated ranking genetic algorithm and the CRITIC-TOPSIS integrated decision method. Finally, the effectiveness of this three-cell grouping strategy in improving the battery storage charging and discharging imbalance and slowing down the losses is verified by comparing with the existing grouping control strategy, and the battery storage configuration schemes under different objectives and different decision methods are compared, and the results show that this multi-objective optimization model and the integrated decision method have obvious advantages in extending the battery life while ensuring the economy.