The treatment of produced liquid from polymer flooding is a significant problem in the oil field industry. Produced liquid from polymer flooding studied in this paper was composed of W/O emulsion and wastewater containing the residual polymer. Alkyltrimethylammonium halides (C(12)TAB, C(14)TAB, C(16)TAB, and C(18)TAB) and dialkyl-dimethylammonium halides (DC(12)TAB, DC(16)TAB, DC(18)TAB) were used both as the demulsifier for the W/O emulsion and as the flocculant for the wastewater. The demulsification tests showed that C(16)TAB is the best performing demulsifier for the W/O emulsion of these cationic surfactants and its water removal can reach 91% at the dosage of 150ppm. The results of interfacial tension and interfacial dilational modulus showed that C(16)TAB had a rapid migration of surface-active agents to the water/oil interface and can lower the film strength significantly at the same time. Therefore, the C(16)TAB can have the best demulsification performance. In addition, C(14)TAB and C(16)TAB exhibited much better flocculation performance than the other surfactants. After the treatment with C(14)TAB and C(16)TAB, the oil content in wastewater decreased significantly to the 30ppm because C(14)TAB and C(16)TAB can move to the oil/water interface and destroy the stability of the oil droplet in wastewater easily, which can be confirmed by the results of zeta potential.