The invention discloses a preparation method of a graphene-cerium oxide hybrid material, which comprises the following steps: (1) mixing graphite powder and sodium nitrate, adding concentrated sulfuric acid and potassium permanganate in sequence, stirring and mixing, heating, and then adding Ionized water, add hydrogen peroxide solution dropwise, filter while hot, wash the precipitate, and dry it in vacuum to obtain graphene oxide; (2) Dissolve CeCl3·7H2O in deionized water to obtain solution A; dissolve sodium hydroxide in deionized In ionized water, solution B was obtained; solution B was added dropwise to solution A, filtered, the precipitate was washed, and vacuum-dried to obtain cerium oxide CeO2; (3) Dissolve graphene oxide in deionized water and ultrasonically disperse; then add cerium oxide Stirring, continue the reaction after microwave heating, filter, wash the precipitate, and dry it in vacuum to obtain a graphene-cerium oxide hybrid material. The method is simple to operate, and the prepared graphene-cerium oxide hybrid material has high degradation activity to ammonia nitrogen.