This work focused on the effects of concentrations of alkali Na₂CO₃，nonionic surfactant BJN-01 and inorganic salt on the dewatering ratios and the apparent viscosities of heavy oil-in-water emulsions. The action laws and synergistic reaction mechanism of the compound systems on the stabilities and rheological properties of emulsion were analyzed. The results showed that the emulsion with 500 mg/L alkali concentration and 0.5% emulsifier volume fraction was the most stable，and its dewatering ratio was 60.7% after standing for 19 h at room temperature. Furthermore，its apparent viscosity was lower，which was 86.2 mPa·s at 30℃ and 20.4 s-1. But adding NaCl into the system could reduce the stability of the emulsion. The higher salt concentration，the greater dewatering ratio was. For the system with 0.5% emulsifier volume fraction and 500—6000 mg/L alkali，the stability of emulsion decreased and its apparent viscosity increased with increasing dosage of alkali. However，for the system with 500 mg/L alkali and 0.5%—0.9% emulsifier volume fraction，the stability of emulsion strengthened and its apparent viscosity increased with increasing dosage of emulsifier.