Aiming at the complex working environment and high failure rate of the gear transmission system,the dynamic analysis of the transmission system was carried out and the failure mechanism was explored. Considering the centrifugal force of the bearing steel ball,the time-varying stiffness model of the deep groove ball bearing is established according to the Hertz contact theory. The time-varying mesh stiffness of normal and crack-containing gears is obtained by the energy method. The gear-bearing coupling dynamics model of the gear transmission system is established by the lumped parameter method.Considering the parameter excitation factors such as transmission error and time-varying stiffness of the gear transmission system,the dynamic characteristics of the gear transmission system are simulated and analyzed,and the Vibration acceleration of the transmission system is obtained. The influence of crack failure on the dynamic response of the gear is analyzed. The correctness of the model was verified by bench test. The results show that the established dynamic model can well describe the dynamic characteristics of the fault-containing gear transmission system. In the time domain waveform diagram,a periodic shock signal is generated due to the presence of a crack fault,and a sideband is generated around the meshing frequency in the spectrogram.