Abstract: Owing to residual hydrolyzed polyacrylamide, oily wastewater produced from polymer flooding was difficult to be treated for its high viscosity and emulsified characteristics. Cationic water clarifier, currently used at increased dosages, can destabilize the polymer in oily wastewater, thus resulting with a large quantity of viscous oily sludge. To settle this problem, a novel amphoteric clarifier QS-01 was synthesized. The experiment results showed that: when the water clarifier was dosed at 130 mg/L and above, the treated wastewater was clear and even colorless with the residual oil concentration decreased dramatically from 5 000 mg/L to 45 mg/L; QS-01 exhibited excellent water-clarification effects at a wide range of temperature from 50 ℃ to 80 ℃; in scale-up assessment experiments, QS-01 also showed satisfying performance with the bright and clean resultant aqueous phase, and the flocs with good fluidity and low viscosity. The mechanism analysis revealed that QS-01 could decrease the thickness of the oil-water interface electric double layer and the strength of interfacial film, and thus weaken the electrostatic neutralization interactions between the clarifier and the anionic polymer in wastewater. It indicated that the problem of viscous polymer-containing oily sludge could be avoided by QS-01.