The design theories of basic rack tooth profile and mathematical model of the double involutes gear are established by using the mesh theory.The formula of the end face and the contact line are also deduced.The mesh process of end face and the change of contact line are simulated.Based on ANSYS

the single teeth mesh FE model and double tooth mesh FE model of double involutes gear with ladder-shape teeth are accurately established by using APDL respectively.The results show that the contact line of double involutes gear with ladder-shape teeth is broken.And the maximum contact stress of single tooth mesh is much larger than double tooth mesh.