The voltage harmonic is an important indicator to evaluate the power quality of PM wind generator. Voltage waveform is closely related to the degree of the air-gap magnetic field waveforms sinusoidal in the motor, so generator structure optimization to improve the degree of air-gap magnetic field sinusoidal is an effective method to improve the quality of generator voltage waveform. This paper presents a method called pole width modulation method to reduce voltage harmonic of wind permanent magnet generator. Do respectively finite element analysis to traditional surface permanent magnet generator and a new very wide modulation permanent-magnet generator; and then develop two structure prototypes and build voltage waveform experimental equipment to study them. Finite element analysis and prototype experiments show that the pole width modulation method is one of the effective and feasible technologies on reducing the voltage harmonic of PM Wind Generator.