In gas separation, the trade off limitations of polymeric membranes and economical consideration of inorganic membranes motivated the researchers to search for alternative approaches. Membranes with high selectivity and high permeability are required. Different modifications are in practice to improve the performance of membranes like mixed matrix, cross linking, grafting, polymer blending, making composite or hybrid membrane. It will be possible to develop polymeric blend membrane for separating high pressure gas streams at their processing pressure. This advantage could offer cost savings that may provide a new incentive for polymeric blend membranes. This result opens a new tool for studying gas separation by polymeric blend membranes. In this context blending of glassy and rubbery polymer that is Polysulfone and Polyvinyl acetate in dimethyl acetamide solvent, flat sheet membranes were developed with desirable properties. Blend membranes with different blending ratios were synthesized and the developed membranes were characterized by Fourier Transformed Infra-Red Spectroscopy (FTIR), Thermal Gravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FESEM) and Gas Permeability to study the effect of blend ratio on different properties. © Maxwell Scientific Organization, 2014.