Abstract: Aiming at the problem of low energy utilization and system operation safety during the charging and discharging process of battery modules in energy storage systems, we proposed a two-layer dynamic equalization method for battery modules based on state of charge. Firstly, the coupled inductor and Flyback converter were used to build the two-layer structure of the equalization system, and the correlation characteristics among the terminal voltage, equalization current and duty cycle of the battery pack were established. In order to improve the reliable energy supply of battery modules, the system introduces the fault removal function, which realizes the rapid removal of the faulty battery module by changing the on-state of the switching array. Secondly, the large residual capacity of the supplementary battery module was taken into consideration, and the two-layer extreme value method improved by the traditional maximum value method was used to realize the rapid discharge equalization of the supplementary battery pack with the stage of charge (SOC) as the equalization target variable. Finally, charging, discharging and static equalization experiments were designed to compare the traditional most value method and analyze the equalization speed and efficiency of the circuit after normal and fault removal. The results show that the two-layer equalization method proposed in this paper can be adopted to increase the equalization speed by about 10%, and the equalization efficiency of the circuit after fault removal can be up to more than 95%.