The article summarizes the speciality of oil-field produced water and wastewater treatment craft flow in oil-fields and compares applied scopes, advantages and disadvantages of different treatment methods.It also points out problems of oil-field produced water in oil-fields,and especially analyzes the produced water of polymer flooding and three compounds flooding in Daqing Oilfeld.The causes for the difficulties treatment are that the polymer increases wastewater' s viscodity and surfactant strengthen emulsification, and at the end the article points out the effective approaches to this wastewater treatment.