Abstract: The visualized experiments were used to study the mechanism of enhanced oil recovery using three kinds of microorganisms consuming crude oil.The microorganisms consuming crude oil have a tendency to migrate directionally towards crude oil and closely contact with crude oil.The "automatic target seeking" phenomenon of the microorganism consuming crude oil consequently resulted in high concentration of microbes around crude oil.Simulation test showed that high-concentration microbes and the metabolic products could act on crude oil,which was favorable to drive remaining oil.Some suggestions for enhancing oil recovery using microorganisms consuming crude oil are presented.