Considering the permanent magnet synchronous generators with nonlinear, uncertain internal parameters and external disturbances, a nonlinear disturbance rejection control method is proposed to achieve Maximum Power Point Tracking (MPPT) of direct-driven permanent magnet synchronous generators wind power generation system. The Nonlinear Extended State Observer (NLESO) and nonlinear disturbance rejection controller are designed based on a nonlinear smoothing function. NLESO is used to estimate the system disturbance and uncertainty and feed forward to the control input to achieve disturbance compensation, which enhances the disturbance rejection ability of the system. And the astringency of NLESO is analyzed. The simulation results show that the control method not only has the characteristics of fast response and high control accuracy, but also has no overshoot and no chattering phenomenon, so it has great application value in the MPPT control of wind power generation system. This work is supported by Project of the Key Subject of Hunan Education Department (No. 17A006).