The invention discloses a method for preparing MnO2 supported catalysts, an application method thereof and a wastewater treatment device. The preparation method comprises the following steps: manganese acetate is prepared into a solution; one of activated carbon, active aluminium sesquioxide, white silica gel, a molecular sieve, zeolite or diatomite is taken as a carrier and dipped in the solution; and supported solid catalysts are prepared through dipping, evaporation, concentration, drying and roasting. A reactor of the wastewater treatment device is divided into a plurality of reaction spaces by baffles, and the catalysts exist as fluidized beds on every baffle. When the MnO2 supported catalysts prepared by the method are used in the reaction of degrading refractory organic matter through ozone catalytic oxidation, the contact time among the MnO2 supported catalysts, wastewater and ozone is between10 and 120 minutes, and the mass ratio of the adding amount of the catalysts to the wastewater in the reaction is between 1 to 200 and 1 to 20. The MnO2 supported catalysts prepared by the method have the characteristics of easy recovery, high repeat utilization property and high efficiency of catalyzing and degrading refractory organic matters.