Non-equilibrium molecular dynamics was introduced for studying supercavitation mechanism and its drag reduction effect. Flow field details like local density distribution，local cavity number distribution，friction coefficient and gas volume percentage were calculated. The results showed that cavity number criterion is applicable in predicting supercavitation. Low cavity number area and actual cavity area are spatially separated. Velocity was the critical factor on cavity formation. Cavitator shape can affect gas volume percentage in cavity. Supercavitation can bring about 50%—90% skin friction reduction，comparing with cloud cavitation. The results agree with previous numerical simulation，showing the model is suitable for studying supercavitation mechanism in molecular scale and provides a valuable tool for investigating flow details.