Aiming at the characteristic of the formation water of Huaqing Chang 6 reservoir and taking the comprehensive foaming ability as evaluation index, 6 foaming agents were optimized. ZY-1 foaming agent was the optimal foaming agent, and the optimal foaming agent concentration and foam stabilizer concentration were 0.5 % and 764 mg/L respectively. On the basis of the foaming agent optimization result, using parallel cores with approximate permeability contrast，CO2 foam flooding experiment was simulated through 2 injection way. The experiment result showed that underground foaming way, CO2 and the foaming agent injected alternately, had higher plugging differential pressure and better displacement efficiency. The optimal injection slug combination was first 0.2 PV (pore volume) foaming agent solution and then 0.4 PV CO2 gas, and the total injected volume was 0.6 PV.