In order to solve the problem of complex derivation of conjugate tooth profile in harmonic drive, a method based on the trajectory envelope of flexspline is used to solve the conjugate tooth profile, and the different tooth height along the axial direction of the flexspline profile is adjusted to avoid interference between the flexible gear and the conjugate steel gear. In order to analyze the influence of tooth root circle radius and torque on the stress of flexspline, a multi-body contact model was established by ANSYS Workbench to explore the influence of root circle radius and torque on the stress of flexspline. The results show that the sensitivity of flexspline stress to tooth profile parameters is higher than that of torque, because harmonic drive is multi tooth meshing transmission, the stress of single tooth is smaller, and the influence of load on flexspline stress is less than that of tooth profile parameters.