The determination of the condensation rate is of fundamental importance in the applications involving phase change heat transfer. In this work, non-equilibrium molecular dynamics method is employed to investigate the evaporation and condensation between two solid walls. The condensation rate is determined by identifying the number of condensing molecules during the simulation. The calculated condensation rate is found to be proportional to the temperature difference between two solid walls. For same temperature difference between the two solid walls, the condensation rate differs with the average temperature of the fluid. The calculated condensation rate is also compared with those calculated from the Hertz-Knudsen-Schrage equation. The results indicate that the Hertz-Knudsen-Schrage equation underestimates the condensation rate with a deviation around 30%. The possible reason of this deviation is discussed.