Emulsion surfactant flooding is a new chemical flooding method for enhanced oil recovery. Under a certain oilwater ratio condition，this type of surfactant can interact with oil and water and form water-in-oil emulsions with high viscosity，and thus the swept volume may be enlarged. The oil displacement mechanism of the emulsion surfactant is different from the traditional polymer and surfactant，and it could not be reflected by the existing numerical simulation methods and softwares. In order to accurately reflect the oil displacement characteristics of the emulsion surfactant，based on analysis of the laboratory results，the main mechanism of emulsification and viscosity increase was manifested，and the mathematical model for characterizing emulsion flow was built and the corresponding numerical simulation method was realized. The accuracy of the mathematic model and numerical simulation method was verified by the fitting result of laboratory model and the application of field model. Relationship between the enhanced oil recovery effect of emulsion surfactant flooding and the factors of emulsion particle size，permeability and heterogeneity was researched，and the effect of emulsion surfactant flooding and conventional surfactant flooding was compared. The results show that the matching relationship between median grain size of emulsion and pore throat has a great influence on the stability and viscosity of the emulsion. Compared with the conventional surfactant，the emulsion surfactant could further improve oil recovery due to better mobility control.