A copolymer with the performances of being responsive to CO2/N2 simulating, was synthesized by free radical polymerization in aquesous solution, using dimethylamino propyl methyl methacrylamid and acrylamide as the reactive monomers and ammonium persulfate as the initiators. The synthetic conditions with optimum property of CO2/N2 responsiveness were achieved by single factor experiment, which was with the result of molar ratio of AM and DMAPMA being 4:1, mass fraction of monomers being 25%, the dosage of initiator being 0.2% of the total mass of monomers, the ractive temperature being 40癈, the reactive time being 4h. At the first, The structure of the products were characterized by FTIR and 1HNMR. What’s more, The electronic conductivity , Zeta potential and particle size of aqueous copolymer solution on the condition of CO2/N2 were measured, which of the result showed that the products can be highly switchable by CO2/N2 simulating and the process was reversible. A remarkble change of the surface morphology of P(DMAPMA-AM) in aqueous solution between dealing with CO2 and without CO2 were measured. It was showed that the emulsions formed by mixing of diesel and pure water can be emulsification and demusification reversibly on the condition of CO2/N2 when P(DMAPMA-AM) was added to the mixed solution as the emulsifier after carbon dioxide and nitrogen were bubbled through the solution mixed of diesel and water with P(DMAPMA-AM) as the emulsifier.