A deep-sea resonant sandwich linear ultrasonic motor is proposed and designed. We determine the parameter of its structure by finite-element analysis. The piezoelectric actuator adopts compound vibration mode of fifth order bending vibration and second order longitudinal. The mode degeneracy of that is completed. We manufacture the prototype to measure the performance of it. We measure its vibration mode and resonant frequency. The velocity of prototype can reach 264.5 mm/s while the water pressure is 8 MPa and the voltage signal with frequency of 30.30 kHz and voltage amplitude of 150 V.