Abstract: To investigate the influences of tooth roughness on the dynamic characteristics of the planetary gear train,a coupling method between the dynamic loaded-tooth contact analysis and vibration displacements of the planetary gear train is proposed. Taking the planetary gear train in the megawatt-level wind turbine gearbox as the research object,the fractal theory is used to characterize the rough tooth surface. Based on the compliance conditions of gear mesh deformations,the relationship among the dynamic loaded-tooth contact status,the component’s vibration displacements,mesh errors,and friction forces of the rough tooth is established. A dynamic model of the planetary gear train in the wind turbine gearbox is constructed,and the influences of mesh errors and friction forces of the rough tooth on the system’s dynamic characteristics are analyzed. The results show that as the tooth roughness increases,the peak and fluctuation amplitude of the tooth surface load increase,and the dynamic mesh stiffness shows obvious serrations,resulting in reduced load-sharing performance. Increasing tooth roughness reduces the critical speed of the planetary gear train. In the low-speed region,tooth roughness has an excitation effect,while in the vicinity of the critical-speed region,it has a damping effect. Friction forces mainly affect the vibration displacement of each component in the planetary gear train and change the amplitude of the dynamic mesh force in the less-tooth meshing zone.