The production of styrene tar is high and the price is cheap. However，the utilization ratio of styrene tar is not high and the burning of styrene tar has pollution to environment. In order to enhance the economic value added of styrene tar and provide a kind of low-cost raw material for oilfield development，styrene tar was made into O/W emulsion used in oil displacement process. The emulsification instability coefficient was used as an emulsifier index to select surfactant. The stability，rheology behavior and oil displacement effect of O/W emulsion，that prepared by styrene tar and aqueous surfactant solution，were evaluated. The results showed that O/W emulsion prepared by styrene tar had a good oil displacement effect. The stability of the emulsion was the best when the emulsifier content was 0.3% and the mass ratio of polyoxyethylene ether to alcohol ether sodium sulfate was 1∶1. For the conventional heavy oil with viscosity of 185 mPa·s，O/W emulsion prepared by styrene tar could increase the degree of reserve recovery by 16.7 percentage points on the basis of water flooding. The emulsion prepared by styrene tar could enhance recovery at the later stage of oilfield development with high water cut.