Abstract: This paper deals with the application of ultrasonic fatigue testing technique to the study of fatigue life and fatigue crack growth behavior of metals and alloys under vibrational excitation at high frequency (20kHz).The mechanical damage and fracture mechanism of materials were investigated in the case of ultrasonic fatigue cycles.This testing technique has remarkable advantages in time-saving,economy and noiselessness and capability for investigating mechanical damage models of aeroengine and rocket structures in real service.