Abstract: Research results show that polymers are subjected to the long-term impacts of various factors after they were injected into the underground, and their structures and properties have changed greatly. In this paper, the producted sewage was exemplified from the production well W7-4 in Bohai Jinzhou 9-3 oil field after polymer flooding. Subsequently, the influences of the produced polymer concentration and remaining oil saturation on oil displacement efficiency were quantitatively evaluated based on the comprehensive analysis of the reservoir geologic characteristics and the observation of polymer molecular morphology with an environmental scanning electron microscope (ESEM), thereby provided guidance for the reutilization of polymer-contained sewage. ESEM photos show that the residual polymer assumes the reticular structure. In addition, evaluation experimental results revealed that polymer-contained sewage flooding can increase the oil displacement efficiency by 1.5%-5% than the common sewage flooding and the efficiency increases with the residual polymer concentration. the higher the remaining oil saturation, the larger the oil displacement efficiency.