The immersion ultrasonic crushing device under 20 kHz is investigated in this study. Combined the sound field analysis and the finite element method, we firstly examine the acoustic mode properties of ultrasonic crushing material cavity on different sound field conditions, i.e. the height of liquid level and the position of sound source, and then explore the distribution of ultrasonic cavitation field and the change laws on the average acoustic energy density. Finally, experiments with acoustic measurement methods and image acquisition are made to verify these explorations. Experimental results shows that the distribution of ultrasonic cavitation field is related to the acoustic modal properties of the sound field. With the value of material cavity radius fixed, when the liquid level reaches the resonant of material cavity at height, the average acoustic energy density in the field is higher and the cavitation effect is significantly enhanced, and the distribution of ultrasonic cavitation field is found similar to that of the material cavity sound field. In the resonance level, the position of the sound source has obvious effect on the average acoustic energy density and cavitation enhancement.