The purpose of this research is to study of flow characteristics of microbubble generator. Using nozzles create small bubbles by ejector type microbubble generator. A cylindrical tube within the channels for fluid flow that is designed to extend and reduce the area of steps so that the complex pressure change along the flow. Air is sucked by the most automatic dropping pressure point. The air is reduced to a number of microbubbles by the cavitations. In the experiment, considering the effect of diameter of the liquid inlet and position of the air inlet.