Aerospace planetary gearboxes are subject to wear on the gear tooth backlash after long service cycles. Tooth wear induces changes in the friction force and causes abnormal vibrations in the planetary gearbox. Under the condition of high rotation speed in the aviation service environment, the dynamic friction even damages aerospace electromechanical actuators. To investigate the nonlinear vibration mechanism induced by the friction coefficient at different wear degrees, the tooth friction model is developed, and the time-varying nature of the friction coefficient during gear meshing and the dynamics of the friction force during wear are analyzed. A torsional dynamics model of a planetary gear system using the concentrated parameter method is established. The tooth friction model is integrated into the torsional dynamics model and the friction dynamics model of planetary gears is established. The friction dynamics model is nondimensionalized and solved by using the fourth-order Lunger Kuta method. Then the influence of the dynamic friction on the vibration characteristics of the planetary gear system is analyzed for different wear degrees under the action of external excitation speeds and verified with experiment. This paper provides theoretical guidance for early monitoring of gear wear degrees and extending the service life of aerospace planetary gearboxes.