Abstract: The spatial distribution characteristics of the ultrasonic cavitation effect are studied when applying 20 kHz ultrasound on the sound field of a cylindrical reactor to form acoustic flow phenomenon. Combined with the acoustic radiation force from large amplitude sound source, the acoustic flow phenomenon of sound field is studied through simulation analysis. The velocity field distributions of acoustic flow under different ultrasonic powers and liquid level heights are obtained, and the motion distribution law of cavitation bubble under the condition of acoustic flow is preliminarily explored. The sonochemiluminescence experiment of ultrasonic cavitation effect is conducted to study the spatial distribution characteristics of ultrasonic cavitation effect under the condition with and without acoustic flow. The results are shown as follows: when the power amplifier current is higher than 80 mA (the electric power is 17.6 W), stable acoustic flow phenomenon forms in the ultrasonic field, which can effectively improve the acoustic energy radiation efficiency, greatly increase the cavitation effect area, and thereby improve the sonochemical reaction efficiency. The distribution area of ultrasonic cavitation effect in the reactor is related to the ultrasonic power (amplitude) and the height of the liquid level: when the current of power amplifier is increased from 40 mA (electric power 8.8 W) to 120 mA (electric power 26.4 W), the proportion of cavitation area increases by 100.86%, and for the liquid level is 60 mm, the cavitation area proportion increases by 13.11% and 73.91% respectively compared with these for the liquid levels of 50 mm and 70 mm; the diffusion distance of cavitation bubbles can be effectively increased and the cavitation distribution area can be increased by increasing the ultrasonic power and selecting the reasonable liquid level; for the reactor with fixed shape and size, when the acoustic flow velocity reaches a certain threshold, the cavitation effect will be enhanced, and the area of cavitation effect enhancement is located in the region where the acoustic flow velocity is greater than the threshold; the main diffusion distribution of cavitating bubbles is closely related to the acoustic flow velocity field; there are three kinds of diffusion patterns: radial diffusion in the middle of the reactor, diffusion along the axial direction of the horn and radial diffusion at the bottom of the reactor, as well as diffusion along the axial direction of the horn.