In this study, polymeric membrane was prepared by using supercritical fluid extraction(SFE) method. Calcium carbonate(CaCO₃) particles impregnated in silicone rubber network were extracted by using supercritical carbon dioxide. When supercritical carbon dioxide diffused through a composite sample, the sample was swollen. CaCO₃ in silicone rubber network was dissolved in supercritical carbon dioxide, and its sites become pores. The pore distribution of silicone rubber-CaCO₃ was controlled, varying amounts of CaCO₃ extracted. Pore distribution and shape were observed by SEM and specific surface area was measured specific surface area analyzer. The performance of porous membrane was tested by permeability of gases such as carbon dioxide and oxygen. Permeability coefficient(P) of carbon dioxide and oxygen was measured by the volumetric method proposed by Barrer. According to the result of this performance test, the optimum condition of silicone rubber membrane was 277 bar at 308.15K. To measure the gas permeability coefficient, the silicone rubber membranes were prepared at 308.15K. As the extraction pressure increased, the gas permeability coefficient of carbon dioxide increased more than that fo oxygen. Also, in the range of pressure above 277 bar, membrane selectivity was greater than 2.5 for CO₂/O₂.