The rotor eccentricity of permanent magnet wind generator will cause uneven distribution of generator air gap and magnetic field imbalance, which aggravate the vibration of the generator, and even cause rotor scrapping in serious cases and result in generator damage and failure. Taking a MW-class permanent magnet wind generator as the analysis object, the influence of air gap eccentricity on generator air gap flux density and radial electromagnetic force is analyzed theoretically. Finite element analysis of transient electromagnetic field of wind generators under different air gap eccentricities is performed, and the distribution characteristics of air gap flux density and radial electromagnetic force under different air gap eccentricities are obtained. Harmonic response analysis of the stator under the radial electromagnetic force is conducted to obtain the response characteristics of the stator caused by air gap eccentricity. The results show that with the increase of air gap eccentricity, the amplitude of air gap density is increased, and new side band components of radial electromagnetic force appear. The amplitudes of harmonics of the operating frequency in the vibration response of generator stator also increase, and the amplitude of the second order radial mode response is the largest. The results can provide a certain theoretical basis for the research of generator air gap monitoring method.