Abstract:A dynamic model of planetary gear system including random backlash, friction, timevarying meshing stiffness and other factors affecting gear vibration is established. The nonlinear dynamics method is used to solve the equation, and the influence of excitation frequency on the system is analyzed. The active noise reduction measures of profile modification are proposed, the system is improved, and the dynamic equation of planetary gear system is recalculated. The influence of the excitation frequency on the improved system is solved and analyzed, and compared with the results obtained by the original system, it can be seen that the modification is effective for the vibration reduction of the gear system.