Abstract: In the alkali-polymer pilot test of Yangsanmu oilfield, scaling often led to surface pipeline plug and polymerdegradation while preparing combination flooding system with produced sewage. A new active alkali with strong capacity of calciumand magnesium scale resistance and decreasing interfacial tension was adopted to prepare with produced water polymer. This paperdiscusses the oil-displacement capacity when different alkali matches with polymer, and whether binary system flooding can be carriedout when viscosity of crude oil reaches 530 mPa·s. Research indicates that oil-water interfacial tension reaches magnitude of 10 － 3,and recovery factor with binary system flooding increases about 17% compared with pure water flooding, at oil viscosity of 530 mPa·sand alkali-polymer binary solution viscosity of 45 mPa·s prepared with produced water. Given crude oil viscosity and ultra-low oilwaterinterfacial tension, once the system concentration exceed technologic critical point, continuous increase of solution viscositywill not obtain the large increase of recovery factor. The research provides a powerful technical means for enhanced oil recovery withchemical flooding in the late stage of water injection development in ordinary heavy oil reservoir.