: In this research، a gas separation property of polyvinyl amine -polyurethane membranes , also effect of silica nanoparticles on the gas permeation properties of polyurethane-polyvinyl amine has been investigated. polyurethane based on hard segment consisting of isophoronediisocyanate (IPDI) , 1،4-butanediol , but,amine , soft segment of poly(tetramethylene glycol) (PTMG) ، were synthesized. The polymer was synthesized in mole ratios of 3:2:1 of diisocyanate: chain extender: polyol by bulk two-step polymerization. Polyvinyl amine was synthesized trough hafman reaction. PU-PVAm membranes were prepared by thermal phase inversion method. Physical properties of synthesized polyurethanes , polyvinyl amine , polyurethane-polyvinyl amine membranes were investigated by FT-IR , SEM. Results obtained by FT-IR indicate that there is an interaction between polyurethane free carbonyl group , amine functional group in polyvinyl amine. SEM micrographs confirm that interaction between polyurethane , polyvinyl amine is weak , polyvinyl amine stay on the surface of the membrane , do not penetrate into the bulk of the polymer. The permeability of nitrogen، oxygen، methane , carbon dioxide were determined using constant volume method at the different pressure , temperature.The results of gas permeation experiments represented that by increasing the polyvinyl amine content in polymerstructure، permeabilityof the non-polar gasesdecreased , co 2 permeability , selectivity increased. It has been observed that the selectivity of CO 2 gas over N 2 , CH 4 in polyurethane considerably increased. Permeability of CO 2 was increased from 331 barrer in pure polyurethane to 531 barrer in the membrane containing 10 wt% of the polyvinyl amine. Furthermore.the selectivity of CO 2 /N 2 in the corresponding membranes demonstrated an increase from 20 to 197i the polyurethane-polyvinyl amine membranes. The gas separation performances of the prepared polymers have been comprised to Robeson upper bound. As shown the polyurethane – polyvinyl amine membranes have high performance in separation of CO 2 . olyurethane-polyvinyl amine silica Nano composite membranes were prepared by thermal phase inversion method. The prepared membranes were characterized using SEM. The obtained SEM micrographs confirmed that the silica nanoparticles increased distribution of polyvinyl amine in polymer matrix. Gas permeation properties of polyurethane-polyvinyl amine silica Nano composite membranes with silica content of 1،5 , 3 wt.% was studied for pure gases at different pressure. The obtained results indicated the increment in permeability of all non-polar gases،, reduction in co2 permeability , also CO 2 /N 2 ، CO 2 /CH 4 , O 2 /N 2 selectivities by increasing the content of silica nanoparticles in polyurethane-polyvinyl amine silica membranes. : In this research، a gas separation property of polyvinyl amine -polyurethane membranes , also effect of silica nanoparticles on the gas permeation properties of polyurethane-polyvinyl amine has been investigated. polyurethane based on hard segment consisting of isophoronediisocyanate (IPDI) , 1،4-butanediol , but,amine , soft segment of poly(tetramethylene glycol) (PTMG) ، were synthesized. The polymer was synthesized in mole ratios of 3:2:1 of diisocyanate: chain extender: polyol by bulk two-step polymerization. Polyvinyl amine was synthesized trough hafman reaction. PU-PVAm membranes were prepared by thermal phase inversion method. Physical properties of synthesized polyurethanes , polyvinyl amine , polyurethane-polyvinyl amine membranes were investigated by FT-IR , SEM. Results obtained by FT-IR indicate that there is an interaction between polyurethane free carbonyl group , amine functional group in polyvinyl amine. SEM micrographs confirm that interaction between polyurethane , polyvinyl amine is weak , polyvinyl amine stay on the surface of the membrane , do not penetrate into the bulk of the polymer. The permeability of nitrogen، oxygen، methane , carbon dioxide were determined using constant volume method at the different pressure , temperature.The results of gas permeation experiments represented that by increasing the polyvinyl amine content in polymerstructure، permeabilityof the non-polar gasesdecreased , co 2 permeability , selectivity increased. It has been observed that the selectivity of CO 2 gas over N 2 , CH 4 in polyurethane considerably increased. Permeability oane