Abstract: The parameters that can effect CO2-alternating-water flooding development are more.In order to obtain the optimal development effect,by taking A well group as the research object in ultra-high water cut development stage,with the numerical simulation method,the parameter optimization of CO2-alternating-water flooding has been carried out and therefore,a set of ideas and methods of CO2-alternating-water flooding and EOR have been established.The results show that the implementation of CO2-alternatingwater flooding can make high water cut decrease 5% ~10%,increase oil production,maintain a stable formation pressure and maintain economic and effective oil well production for a long time.