Maximum Power Point Tracking (MPPT) is an important means to improve efficiency of PV power systems. The simulation model achieving MPPT of independence PV power system, BOOST circuit as the core, is established. The model can simulate the implementation of PV arrays and MPPT without exact characteristics and parameters of the internal circuit. The simulation results show that the closed-loop system can track the maximum power point of PV and work stably in the maximum power point. It can fast track to the corresponding maximum power point in the case of environment changes. The requirements of steady and accurate of auto follower system are achieved.