To verify the rationality of the passive side bias speed limiting mechanism in small and medium-sized wind turbines, a data processing method was proposed for the processing of the measured data of small and medium-sized wind turbines, which adopts the isolated forest method to screen out the error-distorted data for pre-processing, and then applies Bion's method for the selection of the data, and uses the polynomial fitting method for the curve-fitting method, with polynomial fitting coefficients determined by the least-squares method. Obtain the processing method for the wind power curve of WTGs with passive side biased speed limit. The passive side deviation speed limiting FD4.0-2kW/10 WTG was selected for example analysis to demonstrate the validity of the data processing method, and the relationship between the wind energy utilization rate and the tip speed ratio was established, and the performance of FD4.0-2kW/10 WTG was analyzed and it was concluded that the output power of the unit starts to decrease when it is above 13 m/s, which indicates that the design of the side deviation speed limiting mechanism of the unit is reasonable and the security is. It shows that the unit's side deviation speed limiting mechanism is reasonably designed and has high safety.