The invention discloses a Fenton-like reagent, and a preparation method and application thereof. According to the reagent, molybdenum oxide quantum dots and hydrogen peroxide are taken as raw materials, and the molybdenum oxide quantum dots replace metal salts such as ferric salt and the like in conventional Fenton reagents to catalyze hydrogen peroxide to generate free radicals to oxidize and degrade organic pollutants. The reagent is used to degrade organic pollutants, then the problem that subsequent treatment is high in cost and difficulty due to the fact that metal salts such as iron salt, manganese salt and the like easily generate metal sludge precipitations is solved, and reaction efficiency and utilization efficiency of hydrogen peroxide are both greatly improved. Meanwhile, the Fenton reagent has high reaction activity in a wide pH range, an extreme acidic environment is not needed, and the service life of equipment is prolonged while cost is reduced. Therefore, the Fenton reagent can improve degrading efficiency of a Fenton technology on organic pollutants, reduce treatment cost and expand the application range of the technology, and has a good application prospect.