Abstract: As the dilution method changes from clean water to produced water in Daqing oilfield, the powder HPAM consumed is increased by about 40 % -65 %, resulting in the decreased technical effects and economic benefits of polymer flooding. In addition, the method leads to a time-consuming preparation of powder HPAM and massive ground investment. Reducing the amount of polymer used, improving the effectiveness of polymer flooding technology, quick dispersion and dissolution, as well as lower investment in surface facilities are particularly important for enhancing the quality and efficiency of polymer flooding. Based on systematic evaluation of physical and chemical properties and oil displacement effect of emulsion polymer (E-AM/AA/AMPS), the results compared with powder polymer (P-HPAM) indicate that the emulsion polymer has better viscosifying capacity, viscosity stability, anti-shearing property, interfacial performance and emulsifying ability. When the method of preparation with clean water and dilution with produced water is used in the natural core oil displacement experiment, at the same polymer concentration of 1600 mg/L and consumption of 960 mg/L, the enhanced oil recovery (EOR) of emulsion polymer flooding is 18.8 % OOIP, 6.9 % more than that of dry polymer flooding. When EOR is about 13 % OOIP, the dosage of emulsion polymer is 1080 mg/L, lower than that of dry polymer. The emulsion polymer can be completely dissolved in 20 minutes, accouting for 1/4 of the dissolution time for dry polymer, thus realizing online ripening and simplifying the preparation and injection process. At present, the field test of emulsion polymer flooding has witnessed a significant effect of oil increase and water reduction.