The thermophilic bioemulsifier-producing bacteria，Geobacillus stearothermophilus SL-1，was chosen as target species to study growth characteristics and tendency on interface. Simultaneously，the experiment of the displacement effect and mechanism of residual oil after water flooding with strain SL-1 were carried out by microscopic simulation visual model. The results reveal that Geobacillus stearothermophilus SL-1 has hydrocarbon degradation activity using crude oil as sole carbon source. Under compound extreme environment of high temperature（65 ℃）and high pressure（10 MPa），SL-1 bacteria can multiply and metabolize with crude oil so as to degrade oil；biosurfactants produced from the bacteria can emulsify crude oil，change rock surface wettability and disperse residual oil emulsion to oil drops；the oil-water interfacial tension and viscosity of crude oil can be reduced effectively，and the rheology of residual oil may be improved. All kinds of residual oil such as membrane residual oil，columnar residual oil and blind end residual oil have been displaced effectively.At last the oil recovery rate was increased by 12.84%.