The invention relates to a method for preparing a porous carbon material and a treatment method for treating oil-containing sewage. The preparation method comprises the following steps: (1) adding sodium sulfosalicylate into a tube furnace, and calcining at the temperature of 800-900 DEG C in an inert atmosphere for at least 2 hours; and (2) cooling to room temperature, grinding, adding the product into deionized water, adding diluted hydrochloric acid, ultrasonically dispersing till the mixture is uniform, stirring, washing till the mixture is neutral, filtering, drying, and fully grinding, thereby preparing the pure porous carbon material. The porous carbon material is prepared from sodium sulfosalicylate for the first time and has the characteristics of stable structure and performance, uniform pore size distribution, high porosity, novel open pore channels and the like; oily water is effectively treated by porous carbon provided by the invention, so that the concentration of the oily water can be greatly reduced, and the national requirement on environment-friendly blow-off water in China is met.