It is based on double Buck Converter of super-capacitor charging technology. Firstly, double Buck circuit topology and working principle are given, on the base of working principles is introduced, and it is analyzed the soft-switching condition detection research, critical current control and interleaved control strategy; then, it is used Matlab/Simulink software for theoretical analysis simulation verification; finally, in accordance with the theory and simulation, it is completed the hardware and software design and make an experimental Prototype. The simulation and experimental results showed that the control scheme of this paper was feasible and achieve constant current charging for super-capacitor in the critical current mode.