In order to improve the vibration and noise of planetary gear reducer of automatic tapping machine,and improve the tapping accuracy and service life,the transmission contact points of the reducer of automatic tapping machine were tested,and the reducer was simulated with Romax software.The results of test and simulation analysis show that the engaged gear has obvious eccentric load.In view of the above analysis,a compound modification method based on genetic algorithm was proposed,which combined axial modification,.involute modification and tooth profile modification.After modification,the reducer was remodeled and simulated again,and the vibration and noise detection test-bed of planetary gear reducer was built.The prototype was tested before and after the modification.The results show that:after the modification,the problem of partial load in meshing of the gear reducer is improved obviously;the peak load of the gear surface is reduced by 11.75%,the maximum contact stress is reduced by 29.62%,the transmission error is reduced by 35.71%,and the overall vibration and noise of the gear reducer are significantly reduced.