The function of gear transmission is to transmit motion and torque between two weeks. It is one of the most widely used mechanical transmission modes in modern equipment. Its transmission is more accurate, efficient, compact, reliable and long life. The main reason of traditional gear tooth failure is the unreasonable design parameters of gear. The main reason is that the modulus of the gear is small, which will make the bending stress of the tooth root larger. The hardness of the gear pair will not match, resulting in contact fatigue spalling.This paper mainly introduces the fault analysis method of gear broken tooth, makes an in-depth study on the parametric modeling of gear system, and carries out simulation analysis combined with parameters and software. This paper first discusses the important position of gear train in machinery, and introduces the significance of studying and analyzing the fault signal diagnosis method of gear train. Secondly, the dynamic model of gear system is established, and the dynamic model of gear system based on vibration theory is established. Finally, the expression of the meshing stiffness of the gear pair is derived, and the spectrum response characteristics of the system are obtained through the simulation analysis of the model. On this basis, MATLAB software is used to simulate and analyze the gear tooth fracture fault.