The oil/water interfacial properties of crude oil emulsions formed by alkaline/surfactant/ polymer (ASP) fl ooding in the Daqing Oilfi eld were investigated in this paper by the measurement of interfacial tension, interfacial shear viscosity and Zeta potential of the oil/water system. The result showed that both NaOH and Na₂CO₃ could react with acid substances in the crude oil to produce interfacially active components, which are adsorbed on the interfaces between the aqueous phase and oil phase, resulting in a decrease of the interfacial tension, negatively charging the surface of oil droplets, but making little change in the interfacial shear viscosity. For the same ionic strength of NaOH and Na₂CO₃, the interfacial tension of NaOH solution-crude oil system is lower, but the interfacial shear viscosity of NaOH solution-crude oil system is higher, than that of Na₂CO₃ solution-crude oil system. The negative value of the Zeta potential on the surface of the oil droplets is large. Accordingly, the O/W emulsion of NaOH solution-crude oil system is more stable than that of Na₂CO₃ solution-crude oil system.