The transport behavior of oxygen in a poly(dimethyl siloxane) (PDMS) membrane has been studied using a pseudo-nonequilibrium molecular dynamics (MD) simulation. We used three-phase models: The one is the 'permeation modei' discribing the gas/membrane/vacuum-system, the other is the 'sorption model' concerning the gas/membrane/gas-system. In both models, the adoption of the virtual liquid molecules, which have no interaction with the gas molecules, allowed the control of the system pressure that led to the quantitative transport simulation analogous to the real experiments. The permeation coefficient, the mutual diffusion coefficient and solubility coefficient of oxygen at 298 K were directly obtained from the molecular dynamics simulation using the two models. These calculated transport parameters were comparable to the experimental values. The present method may be useful for obtaining information on the microscopic aspects of the transport process of small molecules both at the interface and inside of rubbery polymer membranes.