Abstract: In this paper, the ultrasonic cavitation phenomenon of single bubble is numerically investigated with an improved initial bubble radius associated with the improved dynamic equation (Rayleigh-Plesse equation) considering the effect of compressible of the micro-bubble. The numerical results indicate that the bubble vibration is very sensitive to some exciting parameters. Enhancing the ultrasonic signal frequency can decrease the vibration-initial radius ratio of the bubble. On the contrary, the collapse of bubble will become more violent with higher acoustic pressure, but overhigh pressure will make it never happen. With the increase of bubbles' original radius, the collapse velocity of the bubble becomes higher; the vibration of cavitation bubble can keep on a steady process in a range of initial bubble radius. The cavitation is strongest at the initial radius of 1.6\mum, and will weaken or never happen when initial bubble radius keep on increasing. Enhancing liquid surface tension or viscosity can weaken the collapse of bubble, but the collapse is hard to occur when they become higher. A comparison between the numerical results and the published experimental data shows that the liquid compressibility has a great influence on the determination of zone boundaries of the best cavitation, and makes the cavitation intensity of single bubble stronger.