A one-dimensional model of a short-path (molecular) distillation for two-component systems in the presence of an inert gas was developed based on the weight-not-time-counter Direct Simulation Monte Carlo method. The effect of the composition of the test liquid, the evaporating temperature, the condensing temperature, the distance between evaporator and condenser, the arrangement of distillation space, and the inert gas pressure on mass transfer and separation efficiency is discussed.