Abstract: The reconfigurable battery energy storage system may have inconsistent state of charge(SOC) of the battery pack, which will seriously affect the cycle life of the energy storage system. Therefore, a SOC balancing strategy for reconfigurable energy storage systems based on active balancing technology is proposed. Firstly, a rectification/inversion control method for energy storage inverters is proposed, and the normal operation of the energy storage system's charging/discharging is ensured through the stabilizing and current stabilizing effect of the bidirectional DC-DC conversion circuit. Secondly, a circuit for actively balancing the SOC of an energy storage system is designed. During charging, the energy of the maximum battery pack in the SOC is transferred to the balancing power supply, while during discharge, the energy of the balancing power supply is transferred to the minimum battery pack in the SOC, in order to achieve active balancing of the SOC of each battery pack in the reconfigurable battery energy storage system. Finally, a simulation model is built in Matlab/Simulink to validate the proposed SOC balancing strategy. The results indicate that the proposed SOC balancing strategy can achieve SOC balancing of each battery pack in a reconfigurable battery energy storage system.