The invention relates to a method for treating oily sewage.The method comprises a first step of performing PH adjustment on sewage; a second step of oxidizing the sewage having been treated in the first step; a third step of decoloring the sewage having been treated in the second step; a fourth step of adsorbing the sewage having been treated in the third step; and a fifth step of performing coagulation sedimentation on the sewage having been treated in the fourth step.According to the method, impurities in the oily sewage, such as organic matter and inorganic matter, can be adsorbed and removed efficiently and quickly, the emission of the sewage up to the standard is achieved, a process is simple, a chemical agent is easy to obtain, and the method is low in cost and high in efficiency.