The binary compound flooding can dramatically improve oil recovery after water flooding. In order to have a better understanding of the enhanced oil recovery（EOR）mechanism of binary compound system，the synergistic effect of interfacial activity and emulsifying properties on EOR was studied. The physical simulation experiments，microscopic visualized displacement experiments，and nuclear magnetic resonance（NMR）experiments were applied，with the purpose to study the oil displacement effect of the systems with different interfacial activity and emulsifying properties，to clarify the change law of interfacial activity of the system during the percolation，and to illustrate the synergistic effect of interfacial tension and emulsification on enhancing oil recovery. Results show that because of the reservoir heterogeneity and the performance change of compound system，a lower interfacial tension between the system and oil may not get a better oil recovery. A high interfacial tension is negative to improve the displacement efficiency. However，a low interfacial tension results in an ignorable emulsification effect. When the oil-water interfacial tension and emulsifying properties match well，the residual oil in deep reservoir may be produced at low interfacial tension of the binary compound system. At the same time，oil droplets could plug large throats to change deep flow field distribution and to reduce remaining oil saturation of non-preferred stratum. All of these would reach the aim to dramatically enhance oil recovery.