This study was mainly focused on the mechanism of SRB in EOR. To do this, the whole research was divided into four parts. In the first part, surface activity of SRB metabolites including interfacial and surface tensions, oil recovery rate from saturated oil sand, and effectiveness of emulsification were studied. Many previous studies demonstrated that metabolites produced by variety of microbes could act as biosurfactants to reduce interfacial tension (IFT) between oil and water, and thus improve the solubility and mobility of oil