We report a high performance CO2 capture membrane based on the copolymerization and self-cross-linking of poly(glycidyl methacrylate-g-poly(propylene glycol))-co-poly(oxyethylene methacrylate) (PGP-POEM) comb copolymer. The epoxide-amine reaction is responsible for the self-cross-linking reaction, which takes place under mild conditions without any additional cross-linkers or catalysts. The effects of self-cross-linking on the membrane properties are investigated by comparing the copolymers with those containing a low PPG grafting density (l-PGP-POEM). Furthermore, the gas separation performance of the membranes is systematically investigated as a function of POEM content in the comb copolymer. Both the permeance and selectivity of the PGP-POEM membranes are enhanced simultaneously with increase in the POEM content up to 51.2 wt % (PGP-POEM13), at which the best performance was achieved among the membranes. The high performance results from the reduced diffusion of N-2 due to the self-cross-linked structure as well as the increased CO2 solubility due to the high content of ether oxygen groups in the comb copolymer. By optimizing the membrane thickness, the performance is further improved up to a CO2 permeance of 500 GPU (1 GPU = 10(-6) cm(3) (STP)/(s cm(2) cmHg)) and CO2/N-2 selectivity of 22.4, which is close to the commercialization target area of CO2 capture membranes. This work suggests a simple and economical cross-linking method to fabricate the membranes with excellent gas separation performance.