Abstract: With the development of the Tahe Oilfield, the property of produced fluid changes, which increases the stability of oil/ water emulsion. Consequently, different components, solid or fluid, evenly disperse in sewage, resulting in unstable dehydration. The treatment of simultaneous oil and impurity removal in settler cannot meet the requirement of present production. Therefore, by adopting the processing technology of " removing oil firstly, impurity secondly", oil emulsion in sewage can be utmost eliminated, easing production loading in the settling and filtering sections. This processing technology has gained a successful application in the No. 2 and No. 3 plants of water disposal of the Tahe Oilfield, offering reference for the treatment of oil-bearing sewage which is highly-emulsified and has low oil/ water density difference.