Abstract: Based on the testing results on thermal stability and ability to lower steam mobility of surfactants,this paper systematically studies the effect of structure,molecular weight and concentration of aliphatic α-olefin sulphonate,as well as steam quality,non-condensable gas,electrolyte on foam efficiency.It is found that structure and molecular weight of surfactant are the overriding paramerers to reduce steam mobility during steamflooding,and that the concentration has main effect on foam generation time and little effect on foam efficiency.The addition of small amounts of non-condensable gas is also very important on steam-foam efficiency.The presence of an electrolyte has some side-effects on foam efficicency.