Abstract: Disclosed is a method for preparing a carbonized silk photocatalyst, comprising; soaking a natural silk and an activator in water, taking out the soaked silk, and drying the same; and roasting the dried silk under the protection of an inert atmosphere to prepare a carbonized silk photocatalyst. Also disclosed is a method for photocatalytic desulfurization of a fuel oil, comprising: mixing a fuel oil to be desulfurated, an extraction agent and a carbonized silk photocatalyst, with air being used as an oxidizing agent, to conduct a photocatalytic reaction under light irradiation, and separating an upper oil phase to obtain a desulfurated fuel oil. The catalyst has a simple preparation process, and can effectively reduce dibenzothiophene sulfides, which are difficult to remove, in the fuel oil under UV light radiation. Desulfurization can be achieved at room temperature, and reaction conditions are mild.