By analyzing multi-parameter rotor power coefficient model used in wind generator system, fitting surface function and its nonlinear equations set are established. The nonlinear equations set is converted to the linear equations set by Newton method, and then the linear equations ser is being solved. This paper designs the method of collecting sample data to fit rotor power coefficient of wind turbine. Theoretical analysis proves that this method is effective. The example results show that the rotor power coefficient fitted by the method has high accuracy and better value of engineering applications, and is also suitable for the models of wind generator systems with different parameter perturbation situation.