Abstract: Organ nozzle and Helmholtz nozzle are two kinds of typical self-resonating water jet nozzles. The differences of jet’s characteristics between this two nozzles are determined by different geometric structures. In this paper, the structure characteristics and generation mechanism of self-resonating water jet of the two nozzles were analyzed based on hydroacoustics and fluid network theory. Firstly, the method of extracting the signals directly was employed to collect the flow pressure pulsation signals in the cavities of two nozzles; and then frequency characteristics of self-resonating water jet was analyzed through signal analysis methods. Moreover, striking tests and noise analysis method were combined to analyze the cavitation characteristics of jets from different nozzles. The results show that comparing to ordinary nozzle, both organ nozzle and Helmholtz nozzle can produce high-frequency pressure oscillation and promote the generation of cavitation; however, Helmholtz nozzle has function of amplification on spectrum amplitude and cavitation effect is more obvious on the self-resonating water jet.