Abstract: This paper presents an experimental study on the fluiddynamic processes of water entry of a slender body in some different cases.The impact effect between slender body and water surface after water entryof a slender body are recorded at real time by a high-speed camera. Thedevelopment process of supercavitation which is induced by high-speedslender body is visualized clearly. The oscillation of water surface afterwater entry of a slender body and the instability of the motion of slenderbody in some different cases are analyzed in detail. The velocities ofslender body after entry water are calculated from experiment data.According to our analysis to the variation tendency of the slender body'svelocity, the effect of supercavitation on drag reduction is validated.