At first, the betaine surfactants new 2# for the binary oil displacement system suitable for Changqing oilfield was chosen from the sulfosalicylic-hydroxyl amphoteric surfactant（new1#、new2# and new3#）, whose carbon atomic are 12, 14 and 16, respectively, by determining the interfacial tension between the Changqing crude oil and SP binary system containing 1500 mg/L HPAM and surfactant with different concentration. Using oil sand of Changqing reservoir as adsorbent, the interfacial tensions between the binary system with different surfactant concentration and the Changqing crude oil were determined by means of static oscillation adsorption after multilevel adsorption and the changing trend of interfacial tension was studied. The research results showed that The changing trend of minimum interfacial tension was the same as S-type of adsorption isotherm. With the increase of adsorption times, the higher the concentration of surfactant was, the more slowly the minimum interfacial tension increase. The lower the concentration was, the larger the changing range of interfacial tension was. With the increase of adsorption times, the range became smaller; and the lower the concentration was, the faster the decrease of the range was. The result of displacement experiments indicated that based on the water flooding (oil recovery being of 25%), the oil recovery was increased 10% by injecting the binary system containing 1500 mg/L HPAM and 2000 mg/L new2#, which met the demands of the SP binary flooding in Changqing oilfield.