Abstract: Aiming at improving the utilization ratio of jet, the self-excited oscillation pulsed air-water jet is generated by entraining air into the chamber of a self-excited oscillation pulsed water jet nozzle. The present studies focus on the actual influencing factors of oscillation frequency and hitting power of jet. Based on the theory of hydro-acoustics and fluid dynamics, a theory model which describes frequency characteristic of the self-excited oscillation pulsed air-water jet is presented. Moreover, the time domain and frequency domain characteristics of jet can be obtained by testing the vibration of cantilever beam with equalized strength caused by the jet impinging. The calculation result of the model show that the oscillation frequency of self-excited oscillation pulsed air-water jet monotonously decreases with increasing the cavity length, the relation between frequency and air hold-up is not always decreasing monotonously, but begins to go up after the minimal value. However, the sudden change of the model curve occurs at a given very low air hold-up. The theoretical result is confirmed well by experiment; it is also found that the optimal chamber length corresponding to the maximum resonance peak of the self-excited oscillation pulsed air-water jet is slightly smaller than that of the self-excited oscillation pulsed water jet, and the maximum resonance peak of the former is much higher than that of the latter.