In order to research the effect of emulsifying property of chemical flooding system on enhanced oil recovery（EOR），and reveal the relationship between emulsification comprehensive index and EOR，the oil displacement effect of polymer/surfactant/alkali（ASP）complex flooding system with different emulsion strength was studied. The results showed that it had poor effect on EOR when the emulsification comprehensive index was bigger than 70%. While the emulsification comprehensive index of flooding system was decreased to about 60% by decreasing alkali concentration and emulsification of surfactant，the enhanced oil recovery rate increased from 9.92% to 21%—30%. The best emulsification comprehensive index was about 60% for ASP flooding. The effect of decreasing surfactant’ s emulsification on EOR was bigger than that of decreasing the concentration of alkali.