Nowadays, mixed matrix membranes (MMMs) have considered by many researchers to overcome the problems of polymeric membranes. In addition, molecular dynamics (MD) and Monte Carlo (MC) simulation Methods are suitable tools for studying transport properties and morphology in MMMs. For this purpose, in this study using material studio 2017 (MS) software, the transport properties of CO2, CH4 and N-2 in Pebax, Psf neat Pebax/Psf composite and Pebax/Psf composite filled with ZIF-90 particles have been investigated. By adding Psf to Pebax matrix, the selectivity of CO2/CH4 and CO2/N-2 gases has significantly increased. In addition, adding ZIF-90 particles to the Pebax/Psf composite increased the permeability of CO2, CH4 and N-2 compared to neat and composite membranes. The morphological properties of the membranes, such as the fractional free volume (FFV), radial distribution function (RDF), glass transition temperature (T-G), X-ray diffraction (XRD) and equilibrium density have calculated and acceptable results have obtained. (C) 2020 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.