Abstract: By using a heterogeneous microscopic simulation model which directed at different residual oil distribution characteristics of heterogeneous reservoirs, a study on polymer/surfactant (SP) binary system oil displacement mechanism and efficiency has been carried out. In order to improve the study of SP system, this paper applied the same method to study the oil-displacement mechanism and efficiency of polymer and surfactant. It turned out that the SP binary system has both of the polymer and surfactant system characteristics. It not only promotes the consecutive, cylindrical, membranous and isolated-island residual oil, but also drives the block residual oil which relied on its own higher viscoelasticity and certain emulsification ability. Under the heterogeneous condition, the SP binary system improves the mobility ratio effectively, expand swept volume and start residual oil in low permeability reservoir to a certain degree. What’s more, it also improves oil displacement efficiency basted on the oil-washing capacity of its activator to make the oil recovery improved vastly. This research has great significance in deep research of the composite system displacement mechanism under heterogeneous conditions and field application.