A novel traveling wave ultrasonic motor having a stator with a square hole is proposed, designed, analyzed and experimented. The stator, which consists of a square-hole metal body and four piezoelectric ceramic plates, is elastically deformed by fitting with a rotor with a diameter greater than the inner length of the stator, thereby generating pre-pressure on the rotor for driving. The modal analysis of the stator is carried out by using the finite element method, and the third order mode is selected as the working mode. The relationships between the maximum amplitude of the stator and the excitation frequency, voltage, wall thickness, side length and corner radius are obtained, and the influence of frequency, voltage and pre-pressure on the output characteristics of the rotor is studied. A prototype is made and its output characteristics are tested. The experimental results show that under the signal excitation of 100 V and 31.5 kHz, the no-load speed can reach 215 r/min and the maximum stall torque is 1.58 mN·m.