Polymer flooding sewage was used to dilute polymer solution XingBei oilfield. The low viscosity and poor stability made it unable to reach the injection requirement. A series experiments were made to study the problems. The results showed that Fe2+ and Na+ in the polymer flooding sewage were the major causes which reduced viscosity of polymer solution. Suspended solids and bacteria were the secondary factors. In order to effectively use polymer flooding sewage recycle dilute polymer solution and to make the oil field to achieve the purpose of economic and environmental development, the sewage quality was improved by oxygen exposure and putting flocculent. The viscosity of polymer solution was increased by 10.83 mPa·s compared with untreated polymer flooding sewage dilute, and viscosity loss rate was decreased from 28.4% to 12.16%, reaching the reinjection standard.