In order to effectively block off gas breakthrough channels and improve oil displacement efficiency, two sets SD-4 and SD-5 of foam formulation systems were developed. When pH is 3 and the oil ratio is 60%, the size can swelling to more than 4.1 times, foam half-life is 83 hours and resistance factor is 120 for SD-4 formulation system Field pilot shows that CO2 foam can effectively plugging gas channeling channel, expand the swept volume of CO2 gas, reduce the invalid cycle and improve the efficiency of oil displacement. The injection pressure of test well gas increased 6.0Mpa, connective well show obvious effect of increasing oil and reducing gas simultaneously. The technology shows good prospects for development, and provide refrence for other gas flooding development.