On the basis of explaining the wind turbine's operating characteristics and analyzing the relationship between the wind speed and the power extracted by a wind turbine system with variable speed constant frequency, an on-off control method is investigated for the maximum power point tracking (MPPT) of a wind energy conversion system. In this paper, a mathematic model of a squirrel-cage induction generator control system is established, a decoupling method is employed to achieve the purpose of MPPT, and simulation studies are made with Matlab/Simulink to verify the effectiveness of the purposed algorithm, and the simulation results show that the efficiency of the control strategy.