The simulation techniques have been utilized to investigate the structural, physical and separation properties of penetrant gases including oxygen, nitrogen, carbon dioxide and methane through pure and nanosized silica particles filled polysullone (PSF) membranes. Molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations were performed by employing the COMPASS force held to estimate the diffusivity and solubility of the gases into the membrane. The parameters such as fractional free volume, average cavity size and cavity size distributions of pure and PSF are calculated using an energetic based cavity-sizing algorithm. These parameters for the filled membrane are higher than those of pure PSF and increase with the amount of the filler content and as a result, the diffusion coefficient, solubility and permeability of penetrant gases in silica-filled PSF membranes are greater than pure PSF membrane. The simulated results are in agreement with the available experimental data (C) 2013 Elsevier B.V. All rights reserved