Abstract: To reveal the influence of cracks on the vibration characteristics of a two-stage herringbone gear transmission system, a 48-DOF bending-torsion-axis-pendulum coupling dynamic model of the system was established, taking into account factors such as cracks, time-varying meshing stiffness, backlash, and errors. In the model, the potential energy method was used to calculate the time-varying meshing stiffness of each gear pair in a two-stage herringbone gear transmission system with cracks, and the influence of cracks on the time-varying meshing stiffness of the system was analyzed. The Runge-Kutta numerical integration method was used to solve the problem, and time-domain, frequency-domain, phase diagram, and Poincare diagrams were obtained to characterize the vibration characteristics. The influence of cracks on the vibration of the two-stage herringbone gear transmission system was analyzed. Through experiments, the effects of normal gears and cracked gears on the vibration characteristics of the system were compared and analyzed. The results show that when cracks appear in the gears, the time-varying meshing stiffness of the system decreases, and as the cracks intensify, the time-varying meshing stiffness will decrease. Under the influence cracks, the system demonstrates periodic phenomena, characterized by distinct sidebands proximal to meshing frequency doubling, exacerbating the system’s as the cracks worsen. The experimental corroborate the theoretical analysis, furnishing a framework for the dynamic design of the system.