The invention provides a self-testing heterodyne interference type optical fiber hydrophone hardware circuit and a stability testing method thereof. The method comprises the steps that sinusoidal signals output by an acoustic optical modulator driving source are digitally collected and mixed with local oscillation signals generated in a high-speed digital processor, the effective ranges of frequency deviations are compared through low-pass filtering and spectral analysis, and then the stability of the heterodyne interference type optical fiber hydrophone hardware circuit is judged. The directterminal testing and verification method is high in testing precision, simple and easy, and time and energy are saved; the existing structure of an interference type optical fiber hydrophone system isnot changed, and new interference signals introduced by the acoustic optical modulator driving source and a digital circuit demodulation part are effectively avoided; in the testing method, taking-upand paying-off of an array cable part of the interference type optical fiber hydrophone system do not need to be conducted in water, the array cables are prevented from being damaged, and the testingefficiency is effectively improved. Signal demodulation is conducted by using a digital circuit, the circuit structure is simple, the timeliness is high, the transportability is high, the field programmable ability is high, and real-time programming testing is facilitated.