Abstract: Carburized gears in wind turbines operate under heavy load conditions, with their predominant failure mode being tooth interior fatigue fracture. To explore the impact of quenching residual stress on crack propagation in heavy-duty gears of wind turbines, a three-dimensional numerical model of carburizing and quenching was developed. By considering the alteration in material properties due to carburizing and analyzing the residual stress distribution after quenching, the time-varying meshing stiffness during gear engagement under residual stress was computed. Utilizing the lumped parameter method, a six-degree-of-freedom dynamic model of the spur gear pair was established to derive the vibration response and extract the dynamic meshing force. This force was then transformed into an equivalent moment to determine the stress intensity factor at varying carburizing depths, elucidating the effects of quenching residual stress and carburizing treatment on crack propagation in heavy-duty gears. The results indicate that crack initiation occurs in the transition zone between the carburized layer and the core on both sides of the gear tooth, which is attributed to tensile stress within the residual stress from heat treatment. Residual stress elevates the stress intensity factor by nearly 65%. With the increase in dynamic load cycles, the crack length incrementally extends, and the propagation rate continuously accelerates. Before reaching the optimal carburizing depth, a deeper carburizing depth results in a higher number of cycles, with the increase being more than a linear increment.