An innovative 3D meshing automatic method was proposed for the complex spatial surfaces of spiral bevel gears with root transition fillet. The equations of linear chamfer and cutting edge were derived, and the equations of tooth profile surface and root transition fillet of spiral bevel gear were established by utilizing the principle of spatial coordinate transformation. Combined with the axial section projection theorem and gear meshing principle, the tooth face discrete points of the spiral bevel gear were solved accurately. Considering the geometrical characteristics of the spiral bevel gears and the convergence of stress analysis, the key areas such as tooth root transition fillet were refined in blocks. Then through the node-to-element connection method to realize fast mesh generation. Finally, based on the proposed automatic mesh division technology of spiral bevel gears, a specific example of meshing simulation analysis was completed using finite element software. The results showed that the finite element mesh can be generated quickly within 5–10 s, which greatly improves the efficiency and accuracy of the analysis of spiral bevel gears.