In order to improve the transmission stiffness of harmonic gear drive with short flexspline, a design of harmonic drive with new teeth profile is proposed. The teeth profiles of flexspline and circular spline are designed as double arc profile and its conjugate profile with certain axial inclination angle, respectively, so that the contact area between meshing teeth is improved. The WEDM-LS processes for teeth of short flexspline and circular spline are presented, and 50 prototype harmonic gear drives with tilt tooth circular spline and 1/4 and 1/2 length-diameter ratio are developed, respectively. The results of transmission stiffness experiments show that the transmission stiffness of the new designed harmonic gear driver is increased by 39% compared to that of the previous designed harmonic gear driver without tilt tooth.