A method is developed with a relationship between volume of fluid and velocity and molecular dynamics method.Flow velocity of liquid argon is calculated in simulations of three-dimensional Poiseuille flows and cavity flows.It shows that calculated flow velocities are basically consistent with that obtained from traditional molecular dynamics method.The method can be applied to various kinds of channel flows.For flows driven in square cavities,calculated velocities are roughly the same,but the boundary velocities are varied widely.Accuracy of the new method is better with a faster convergence rate.