Abstract: In order to obtain the transmission characteristics of the two-stage planetary gear systems under the geometric eccentric fault condition, the simulation experiment is carried out. Taking the two-stage planetary gear systems in the MW level wind turbine gear system as the research object, the corresponding virtual prototype is established based on SolidWorks and ADAMS. On the basis of reasonable setting of the simulation parameters, the dynamic simulation of the three states of healthy and second-stage solar wheel geometrical eccentricity of 0.1 mm and 0.2 mm is carried out. The results show that in the two-stage planetary gear systems, the geometrical eccentricity fault of the second-stage sun gear has no obvious influence on the dynamic characteristics of the first-stage planetary gear system, and has a great influence on the dynamic characteristics of the second-stage planetary gear system. In the geometric eccentric fault state of the gear, the amplitude of the fault frequency increases with the increase of the geometric eccentricity, and the amplitude of the meshing frequency and its multiplication decreases with the increase of the geometric eccentricity. The amplitude ratio of the sideband meshing frequency can be used as the basis for determining geometric eccentric faults, and the change trend of geometric eccentric faults can be monitored by this value. The research results can provide a theoretical reference for the geometric eccentricity fault diagnosis of two-stage planetary gear systems.