Abstract: The spreading test of liquid Sn-9 Zn brazing material was carried out to observe the growth and rupture of the brazing cavitation bubble under ultrasonic action. It is concluded that the liquid solder penforms behavior of filling soldering seam and diffuses in the shape of a fan.Through the Matlab language and on the basis of ultrasonic cavitation theory,the growth and fracture of Sn-9 Zn,Sn-0. 7 Cu and Zn-5 Al liquid solder cavitation bubbles were simulated from four aspects of temperature,ultrasonic frequency,initial radius of cavitation bubbles and maximum temperature and pressure when cavitation bubbles collapsed,and the motion of cavitation bubbles was obtained. The results show that the higher the temperature is,the weaker the cavitation effect is. The higher the ultrasonic frequency is,the weaker the cavitation effect is. The smaller initial radius of the cavitation bubble is,the more obvious of the cavitation effect of the cavitation bubble is. The maximum temperature at which cavitation bubbles collapse is directly proportional to the adiabatic index,while the highest pressure at which cavitation bubbles collapse is inversely proportional to the adiabatic index and the temperature of the reaction system. The research results provide a reference for the research and application of liquid solder cavitation effect in ultrasonic assisted brazing.