The oil-water interfacial tension, interfacial shearing viscosity, emulsion stability and viscosity reducing effect were investigated between two kinds of viscosity reducers and Tahe heavy oil. The results showed that the interfacial tension was decreased greatly by the water soluble viscosity reducer, while the interfacial shearing viscosity was mainly affected by the oil soluble viscosity reducer. The water soluble viscosity reducer was beneficial for the formation of the oil-water emulsion. The oil soluble viscosity reducer could improve the emulsion stability and had good viscosity reducing effect. When the oil soluble viscosity reducer was compounded with the water soluble one, the viscosity reducing effect and emulsion stability were greatly improved compared with the single reducer.