On the base of traditional disposal methods of produced water before re-injection in oilfields，such as coagulation and filter，the aeration treatment played a significant role in polymer flooding. In order to establish scientific evaluation method of aeration level in produced water，the reasonable testing method of the dissolved oxygen（DO）was proposed，the relationship between DO and viscosity of polymer solutions prepared by produced water was studied，and how flow conditions affected the oxygen consumption and viscoelasticity was also discussed. The results indicated that the accuracy of colorimetric method depended on the choice of testing tubes. By contrast，the electrochemical probe method performed much better during the water quality analysis. Furthermore，the viscosity of polymer solution increased with increasing aeration of produced water. After the DO in produced water increased from 0.25 to 9.42 mg/L，the viscosity increment could reach 14.88%—19.16%，shear resistance and viscoelasticity of the polymer solutions prepared by the water were also improved in a certain degree. It was obviously that the control of viscosity loss was strengthened when the solution concentration increased. However，the viscoelasticity of polymer solutions was scarcely influenced by the flow conditions of produced water after aeration. The optimum DO in water was about 6 mg/L when the polymer solution was prepared by the produced water in sewage station of Daqing oilfield. The results realized the perfect understanding of the aeration control mechanism from qualitative to quantitative.