Abstract： With the aid of a highspeed CCD camera, the droplet formation and flow characteristics in a  polydimethylsiloxane (PDMS) rectangular microchannel with a width of 125 μm and a depth of 300 μm were experimentally investigated. By changing the volumetric flow ratios of water (dispersed phase) and silicon oil (continuous phase), the experimental data on droplet length, velocity, and generation frequency were obtained. Experimental results show that the dimensionless length of droplet in the microchannel can be well determined by the water/oil flow ratio, and a linear relationship is established between them. It is found that the velocity of droplet is larger than the twophase mixture superficial velocity. Besides, a simplified correlation for the precise prediction of the velocity of droplet was developed. In addition, a model predicting the generation frequency of droplet was proposed. The predicted values agree well with the experimental data within a deviation of approximately ±12%.