In order to effectively provide energy buffer for the battery during the driving of hybrid electric vehicle, the state of charge (SOC) of the vehicle-mounted super-capacitor should be kept within a safe range to prevent capacitor overcharge or insufficient energy. To solve this problem, based on the working characteristics of the vehicle-mounted super-capacitors, we improve the traditional filtering distribution method of vehicle-based hybrid energy storage system. The logic gate control which uses complex algorithm logic and is difficult to design parameters is abandoned, and a simple PI control is used to realize the self-maintenance of super-capacitor power during the operation of electric vehicles. The proposed method is verified by a hybrid energy storage device based on the control of TMS320F2812 and a permanent magnet synchronous motor experimental platform based on hardware-in-the-loop simulation. The results show that this method can not only provide peak load power for the super-capacitor, achieve the "peak load shifting" of the battery, but also keep its steady-state voltage at a stable value, which can meet the energy recovery requirements of the vehicle-mounted super-capacitor for the hybrid electric vehicle.