Abstract: Laboratory study and field experiments show that al- kali - surfactant - polymer flooding is a very effective tertiary oil recovery method in conditions of highly effective surfactants. This paper presents the features of oil displacement of alkali - surfactant - polymer flooding system in heterogeneous oil layers at different interfacial tensions (IFT) and viscosity ratios by using numerical simulation technologies and in combination with laboratory studies. Analysis shows that alkali - surfactant - polymer flooding has larger range of application in heterogeneous oil layers compared with that of polymer flooding. As to alkali -surfactant - polymer flooding in heterogeneous oil layers, both increase of viscosity of alkali - surfactant - polymer system and lower of interfacial tension can effectively enhance oil recovery, while high viscosity is critical to enhance oil recovery. The remaining oil in reservoirs with medium to low permeability can be effectively recovered by using layered injection method or by plugging highly permeable layers after alkali - surfactant - polymer flooding, thus recovery factor can be improved further. The study provides an important basis for understanding oil displacement principles of alkali - surfactant - polymer flooding and establishing field testing program.