Abstract: In this paper, super capacitor-battery hybrid energy storage devices and circuits are designed, which can make super capacitor preferentially discharge when sudden loss of power on the AC side or sudden added load on the DC side, and reduce the shock on battery in DC system and extend battery life. For DC systems of substation, two conditions, the sudden loss of power and sudden added load on different super capacitor capacitances, are simulated. The comparison results show that proposed super capacitor-battery hybrid energy storage devices can not only avoid the capacity waste when battery works alone, but also take good use of high power density and long cycle life of super capacity. In addition, it can be found that the bigger capacity of super capacity is, the longer discharging time is, which satisfy the application requirement. In the end, the actual hybrid energy storage DC system experimental platform is built in laboratory, and the experimental results are basically consistent with simulation results.