Abstract: The Numerical simulation and experimental investigations have been carried out on the drag characteristics and cavity shapes of circular cylinders moving in cavitating flow regime. It is shown that the differences of cavity shapes at different aspect ratios are not apparent, but the differences of drag coefficients at different aspect ratios are apparent. As the flow of an underwater circular cylinder developed from a part cavity to a supercavity, the pressure difference drag decreased, and the viscous drag decreased to almost zero. The total drag was same as the pressure difference drag. At a larger cavitation number, the drag coefficient decreases firstly and then increases with the aspect ratio increasing. At a smaller cavitation number, the drag coefficient has an identical trend. For a given aspect ratio, the smaller the cavitation number is, the smaller the drag coefficient is.