A slender type of ultrasonic motor using longitudinal-torsional hybrid vibration is proposed and investigated in this paper. To acquire the response and mechanical capacity of the assembled and complete hybrid longitudinal-torsional ultrasonic motor, a 3D finite element model has been established by the commercial FE software ADINA. The numerical results agree with the experimental results in terms of the trend and the order of magnitude, meaning that it is easy to evaluate the mechanical characteristics of the motor before prototype manufacture. Meanwhile, the radial, circumferential and axial displacements of the contact nodes can be obtained to simulate the actual elliptical motions of the stator teeth. In addition, the practical contact mechanism between the stator and rotor can be accurately reflected by the stress nephogram of the contact surfaces. This research provides a convenient method for the structure optimization and mechanical capacity prediction of the hybrid longitudinal-torsional ultrasonic motor.