The invention provides a preparation method of a diatomaceous earth-carried polymetal oxide ozonation catalyst, which includes the following steps: diatomaceous earth is soaked in acid, and is then washed with water to be neutral, and after drying, acid-soaked diatomaceous earth is obtained; alkali is then used for corrosion, so that preprocessed diatomaceous earth is obtained; impregnation treatment is then carried out for multiple times, so that impregnated diatomaceous earth is obtained, and after roasting, the diatomaceous earth-carried polymetal oxide ozonation catalyst is obtained. Compared with the prior art, the invention uses alkali for corrosion after the diatomaceous earth is washed with acid, so that active silicate is generated on the surface of the diatomaceous earth, impregnation treatment is then carried out for multiple times to carry out ion exchange, so that metal ions are deposited on the surface of the preprocessed diatomaceous earth, consequently, the ozonation and removal rate of chemical oxygen demand by the obtained ozonation catalyst in sewage, moreover, the dissolution of active components is low, the stability is high, furthermore, the mechanical properties of the obtained ozonation catalyst are high as well, the compressive strength is high, and the diatomaceous earth-carried polymetal oxide ozonation catalyst cannot be easily broken.