Provided is a method for catalytically reducing selenium. Hydrogen peroxide is used as a catalyst, and a reducer is added to a hexavalent-selenium-containing solution for reaction so as to reduce the selenium to elemental selenium, wherein the standard oxidation-reduction potential of the reducer is lower than the standard oxidation-reduction potential of the conversion of the hexavalent selenium to elemental selenium. The present method can further reduce a hexavalent-selenium element-containing selenic acid or selenate solution to an elemental selenium product in one step. In the present method, the hydrogen peroxide effectively lowers the descending speed of the reduction potential of the solution while having a catalytic effect, so that the reduction reaction process is carried out gently, thereby effectively preventing the selenium in the solution from overreducing to generate negatively bivalent selenium ions or compounds thereof, and solving problems such as a low recovery rate caused by selenium overreduction.