NOVELTY - Producing carbon dioxide separation membrane material comprises: adding DM and polyglycol acrylic ester (PEGA) into tetrahydrofuran solvent, adding triggering agent, heating for reflowing in an oil bath, cooling, and baking.    USE - The methods are useful for producing carbon dioxide separation membrane material and producing composite membrane (all claimed).    ADVANTAGE - The method can produce composite plates with sound separation performance to carbon dioxide/methane, carbon dioxide/nitogen and carbon dioxide/hydrogen.    DETAILED DESCRIPTION - Producing carbon dioxide separation membrane material, where the material refers to a membrane material formed by copolymerization and cross-linking of acrylic acid amino ester DM and PEGA comprises: adding DM and PEGA into tetrahydrofuran solvent, adding triggering agent, with the total mass percentage of the DM and the PEGA being 5-90%, the mass percentage of the triggering agent being 0.07-1%; heating for reflowing in an oil bath at 50-90 degrees C for reaction for 10-30 hours; cooling the solution after reaction to normal temperature and pouring it in a non-polarity solvent being blended for sedimentation so as to produce a white viscous polymer; then baking it in a vacuum oven for 20-30 hours at 70-120 degrees C to obtain a light yellow transparent polymer PDM-PEGA.    An INDEPENDENT CLAIM is a method for producing composite membrane comprises dissolving the PDM-PEGA obtained into a solvent, taking xylene dichloride as the cross-linking agent and dissolving it in solvent, mixing the two solutions into a mixed liquid for soaking hollow fiber base membrane or pouring it on a treated polymer flat plate base membrane; drying the membrane at normal temperature, repeating the coating steps for 2-5 times, drying it at normal temperature for 12-24 hours to obtain hollow fiber composite membrane or a flat plate composite membrane, with the coating thickness of 105 microns; and storing the membrane in a dryer at normal temperature.