Bubble size is an important reference index for the utilization of ozone. In order to explore the effect of vibration frequency on bubble size, we independently designed and built an experimental device that can change the vibration frequency and measure the bubble size very easily. This paper describes the design and main structure of the experimental device, as well as the experimental steps in the application process and experimental data obtained through experiments and came up with a method to directly measure the bubble size. It is concluded that the larger the vibration frequency, the smaller the size of the bubble (ie, the higher the utilization of ozone in water).