In order to study the influence of vibration signal transmission path on the fault response of sun gear crack in planetary gear transmission system， a dynamic analysis model of ring gear structure is established by finite element method， and the vibration responses of ring gear with and without transmission path are compared and analyzed， which verifies the time-varying effect of transmission path in the model and the validity of the model. The solar wheel crack fault test is carried out， and the fast spectral kur? tosis （FSK） method is used to reduce noise and extract fault features of the experimental signal， which verifies the accuracy of the simulation results of solar wheel crack fault. The results show that the transmission signal of planetary wheel which only engages with the faulty teeth of the sun gear is considered， and the transmission in the path decreases with the increase of distance. When considering the transmission signals of all planetary wheels， the fault signal appears modulation， which tends to decay or increase with the transmission distance. The research results can provide theoretical basis and reference for fault diagnosis of planetary gear transmission system.