In order to improve the stability of oil-in-water emulsifier for crude oil and solve the problem of demulsification，a kind of polymer emulsifier was synthesized using CO2 responsive monomer，hydrophilic polyether structure and acrylamide（AM）as skeleton. The interfacial activity，emulsification stability and the response to CO2 of the emulsifier were studied. The results showed that polymer emulsifier P-2 had the best emulsification performance，which was synthesized under the condition of room temperature and 87.0∶11.8∶1.2 molar ratio of acrylamide（AM），polyether methacrylate（PAM）and 2-（diethylamino）ethylmethacrylate（DEA）. The O/W emulsion formed by the mixture of 600 mg/L P-2 solution and oil phase had good stability and low interfacial tension. The particle size of the emulsion concentrated at about 700 nm. The emulsifier could respond to CO2 repeatedly， and the demulsification rate of emulsion after injecting CO2 and leaving 48 hrs was up to 87.3% . The CO2 responsive polymer emulsifier P-2 not only had good emulsification stability and CO2 repetitive response performance，but also could achieve rapid and efficient demulsification.