The tooth profile has an evidently influence on the transmission performance of harmonic drive (HD). For the purpose of improving the transmission performance of HD, double-circular-arc common tangent tooth profile (DCTP) as the tooth profile of flexspline (FS) was been used. The parametric equations of DCTP were established by using the arc length, and the conjugate existent domain (CED) and the conjugate tooth profile (CTP) were deduced based on Modified Kinematic Method, moreover, the CED and CTP variable law of HD that utilized the DCTP were studied. The results demonstrated that two CEDs are founded in the mesh process, what’s more, the two conjugate phenomenon and the twice conjugate phenomenon were deduced. The arc radius of the convex tooth profile, the arc radius of the concave tooth profile, the conjugate angle, conjugate domain, conjugate position, conjugate arc length and radius were obviously influenced by the common tangent tooth profile length, the obliquity angle between the common tangent and the symmetric line of the teeth, the coefficient of the radial displacement, and the wall thickness of FS. The transmission quality of HD device, in the research example, was improved by appropriately decreasing the abovementioned structure parameters and meshing parameters.
