The invention relates to the technical field of power detection, and more particularly relates to a sensitivity verification method for an optical fiber partial discharge ultrasonic sensing system, which fills a gap in the verification process of an optical fiber measurement method. A to-be-verified optical fiber ultrasonic sensor TUT and two piezoelectric type acoustic emission sensors RT-0 and RT-1 are combined into three pairs of sensor verification combinations, Tone Burst voltage signals with different dominant frequencies are injected into a signal end of the RT-0 or RT-1 by using an inverse piezoelectric effect, acoustic emission vibration signals are excited on crystal faces of piezoelectric ceramics, and a vibration sounding source propagates through a PMMA organic glass dielectric block to form an elastic wave of an ultrasonic wave band. A voltage signal measured by an optical fiber interferometer sensing system also needs to be reduced to the phase change of the transmittedlight waves in an optical fiber caused by the external acoustic perturbation through a phase carrier demodulation technology; and finally, the sensitivity response characteristics of the to-be-verified optical fiber ultrasonic sensor can be calculated from the electric parameter measurement voltages obtained from three sets of verification tests.