The invention discloses a catalyst taking aluminum oxide as a carrier. The catalyst is prepared from the following raw materials: the aluminum oxide, MoO2, Cr2O3, MnO2, SnO2, ZrO2, a lubricant and heteropoly acid. A preparation method comprises the following steps: adding the aluminum oxide into an electrolyte solution and impregnating; after ageing, transferring a mixture into a hydrothermal kettle; reacting to prepare the carrier; after uniformly mixing the MoO2, the Cr2O3, the MnO2, the SnO2, the ZrO2 and the heteropoly acid, adding the carrier and impregnating to obtain the catalyst. The denitration catalyst has the advantages of relatively low light-off temperature, high thermal stability and high hydrothermal stability, wide activity temperature window and high denitration efficiency, and the service life of the catalyst is long; meanwhile, the preparation method provided by the invention is simple and high in operability and the production cost is reduced.