A regenerative braking system, which could restore kinetic energy and potential energy to a battery or any other forms of power during braking, is a special system for electric and hybrid electric vehicles. However, the large current produced by the generator during braking would affect battery performance and shorten battery life. A hybrid-power system is an excellent energy storage system, in which an ultra-capacitor bank and a battery pack are connected together through a DC/DC power converter. And the ultra-capacitor in this system can store instantaneous large currents quickly, which is able to protect the battery from large currents. The application advantages of the hybrid-power system are analyzed in this paper, as well as a series control strategy for regenerative braking based on it. In order to verify the feasibility of the strategy, a braking force distribution model, which contains one S-Function, between mechanical and regenerative braking is built in MATLAB/Simulink by taking into account the ultra-capacitor voltage, the motor regenerative braking ability and other factors. Simulation results suggest that the ultra-capacitor is able to restore the regenerative energy very quickly, which will improve starting and acceleration performance, extend driving range, and increase fuel economy.