Based on the extended finite element method（ XFEM） and linear elastic fracture mechanics theory,two-dimensional crack propagation calculation program is developed independently with Fortran language,and the accuracy of program calculation is verified. On this basis,the simulation study on the effect of centrifugal force,the initial crack,rim thickness coefficient（ backup ratio） on gear tooth root two-dimensional crack propagation is carried out. The result shows that,the initial tooth root crack location has a great influence on the gear tooth root crack propagation,and the closer of the initial crack position to the center of the tooth groove is,the more likely it is that the rim fracture will occur（ crack propagation along radial）. The rim thickness has a great influence on the gear tooth root crack propagation,and the smaller the backup ratio is,the larger range of the initial crack location is that the rim fracture will occur. The centrifugal force has a great influence on the gear tooth root crack propagation,the larger the centrifugal force is,the more likely the rim fracture will occur,and the larger the initial crack location range of the rim fracture will occur at the same time. This study result has a certain theoretical significance and engineering application value to improve the reliability and ultra-safety of gears in high-speed working conditions.