Inverse demulsifier can effectively improve the interfacial tension of water-in-oil (W/O) or oil-in-water (O/W) emulsions, so that the colloidal particles in the sewage lose their stable repulsive force and attractive force, and eventually lose their stability. Form flocs, and further through chemical bridges, the final completion of the separation of oil and water in sewage and the separation of harmful impurities, to achieve the purpose of recovering oil and purifying the sewage, so as to meet the water quality requirements of the subsequent treatment process or meet the national requirements. Sewage discharge requirements