Fluid flow through channels and ducts in nano scales is an important issue which needs numerical simulations for better analysis of fluid behavior because of the limitations of experimental methods. Hence, in the present study Molecular Dynamics simulation is used as a precise method for molecular scale problems to investigate fluid behavior. This method which is based on Newton’s second law, is applied to investigate liquid Argon flow in steady Couette flows through smooth and rough nanochannels. Using LAMMPS software, were performed simulation. In the present study, the fluid velocity and fluid slip in steady Couette flows were obtained to investigate various effects including: wall velocity, channel height, wall density, fluid-wall interaction, and surface roughness with different shapes such as rectangular and triangular in different dimensions. Based on the results, an increase in wall velocity increases the fluid slip velocity. For velocity constant values, an increase of channel height will decrease the fluid slip velocity. In steady Couette flow, decrease of wall density will result in decrease of fluid slip velocity. Reducing the energy parameter between fluid and wall will increase the fluid slip velocity and on the other hand, decreasing the fluid-wall length parameter will decrease the fluid slip velocity. The rectangular and triangular roughness at the bottom wall reduces the fluid slip velocity, and an increase of roughness height will further decrease the fluid slip velocity.