As peak shaving control were introduced to wind turbine control system, the turbine’s load descended and the distance between the tips and the tower become larger. But generator’s output become more unstable, periodical fluctuation of power carry out much more fatigue injury, which reduced the turbine’s life. Because this is a nonlinear system, the traditional linear system’s analysis method is hard to deal with this problem. This essay provides the mathematical model of the peak shaving control, then analysis the stability of this system with describing function. To enhance system stability, a predictive module based on a differential tracker is used to replace the existing power filter. Simulation experiments have proven the effectiveness and practicality of the stated strategy.