There are problems of nonlinearity, uncertainty parameters and torque disturbance in direct drive permanent magnet synchronous wind power generation systems. Thus a maximum power point tracking control method based on auto-coupling PI control theory is studied. Aiming at speed tracking, the uncertainty of internal dynamics and external input torque of a generator is defined as a total disturbance, and the nonlinear uncertain system is mapped to an unknown linear system, and a controlled error system under the inverse excitation of the total disturbance is constructed. Based on that, an auto-coupling PI controller model based on the error speed factor is designed, and the robust stability and anti-disturbance robustness of the autocoupled PI closed-loop control system are analyzed theoretically. Finally, the simulation results show that the proposed control method can maintain the maximum power factor in a stable fashion. This approach has a good prospect for application in the field of maximum power tracking of a wind power generation system. This work is supported by the Key Project of Hunan Education Department (No. 17A006).