The circuit structure of a Stand-alone PV system based on the super-capacitor energy storage is introduced and the control strategy of bi-directional DC-DC converter is analyzed. The super-capacitor energy storage system based on the fuzzy PI controller is proposed in this paper, the fuzzy PI controller design of the system is discussed, the performance of the system is studied in detail. Finally, the joint simulation with MATLAB and PSIM is made. Simulation results show that compared with classic PI system, the new system based on fuzzy PI controller has better adaptation, better robustness.