Ability and compatibility of the membrane processes for gas separation are evaluated by their membranes’ permeability and selectivity where both have been tried to enhance in promising membrane generation of mixed matrix membranes (MMMs). In the current study, two- and three-dimensional models were constructed for MMMs, and the Fick's first law was solved numerically in them by using the Finite Element Method (FEM) and Computational Fluid Dynamic (CFD) tools. The effects of different MMMs structural parameters such as the volume fraction, size and mode of packing, i.e., regular or random, of the filler particles were investigated on the effective permeability of the pure gaseous penetrants through the MMMs. Furthermore, the interfacial equilibrium constant of the penetrants and their diffusivity ratios were also evaluated in view point of their impacts on the MMMs’ separation performance. Some well-known established models including Maxwell, Bruggeman, Lewis - Nielsen, Pal, and Chiew - Glandt were applied in the modeling. Deviation of the simulation results from the experimentally measured ones were low enough, however, at higher loadings of the filler particles the simulation deviation became greater. Simulated results through PSF - MCM-41 MMMs were compared with those of experimentally measured ones and AAREs of 31.0 (The lowest deviation), 42.7, and 41.0 % obtained for CO2, O2, and N2, respectively.