The composite membrane with high CO2 permeance and high CO2/N-2 selectivity was synthesized by UV-initiated free radical photopolymerization. Both supporting layer and selective layer were fabricated through photopolymerization. The supporting layer was synthesized by poly (ethylene glycol) diacrylate as monomer and polyethylene glycol as pore-forming additive, while the selective layer was synthesized by poly (ethylene glycol) methyl ether acrylate as monomer and dipentaerythritol hexaacrylate as cross-linker. The morphology, chemical structures and gas transport properties of the composite membranes were investigated by different techniques. Resulted composite membranes had defect-free selective layers with high CO2/N-2 selectivity, ranging from 38.8 to 40.9, which were close to the intrinsic selectivity for the selective layer material. In addition, it is found out that the selective layer thickness and permeance were affected severely by varying the consumption of coating solution. The selective layer thickness decreased with the decrement of coating solution consumption, changing from 4.15 to 0.62 mu m, which led to a significant increase in CO2 permeance, ranging from 182 to 1889 GPU (25 degrees C, 0.2 MPa).