Abstract: Self-oscillating cavitating jet is a phenomenon in the process of jet flow. The cavitation is produced by the oscillation characteristics of the internal structure of the nozzle. And the cavitation collapses after it is ejected from the nozzle, which enhances the impact force of the water jet. The selfoscillating cavitating jet effect is related to the nozzle structure. Since Helmholtz nozzle has great advantage in enhancing the jet impacting force, this paper investigates the flow fields inside and outside of the Helmholtz nozzle with different structural parameters based on numerical simulation, and this paper mainly analyzes the influence of some key structural parameters, including the outlet diameter, the outlet length, the resonant cavitating length, the resonant cavitating diameter and the target distance, on the cavitating jet performance, and the results can provide a theoretical instruction for the applications like the caviating jet technology in ship cleaning.