The DC-DC cascading energy storage system features flexible grouping of battery modules. The DC-DC converter is used to finely manage the charging and discharging of the battery modules. By adjusting the charging and discharging power of each DC-DC, the goal of balancing the state of charge (SOC) of the battery is achieved. In the case of cascading battery utilization and mixed use of new and old batteries in power station operation and maintenance, the impact of battery health status (SOH) on the system balancing effect needs to be considered. A SOC balancing method based on droop control is designed. Firstly, construct the structure of the DC-DC cascaded energy storage system and the engineering estimation method for SOC and SOH; Secondly, a mathematical model for series current power droop control is constructed, and the droop coefficient is determined based on the voltage regulation range on the bus side of the DC-DC converter and the output power capacity constraint. Then, a balanced control strategy considering SOH based on droop control is designed; Finally, the SOC balancing effect of eight 14.5kW DC-DC cascaded energy storage systems was verified through simulation and experiments. The results indicate that the inter unit SOC balancing of the DC-DC cascaded energy storage converter considering SOH has a significant balancing effect and speed.