The invention discloses a phosphorus- and potassium-containing aluminum oxide carrier and a preparation method thereof. The aluminum oxide carrier is prepared by molding an aluminum oxide carrier by using aluminum hydroxide gel, which is prepared by a molten-salt super-solubility micelle method, as a raw material at first and then loading potassium and phosphorus on the aluminum dioxide carrier in a spraying and soaking mode. In a process of preparing the carrier, the aluminum hydroxide gel has a surfactant and hydrocarbon components, so that after the aluminum hydroxide gel is molded and roasted, aluminum oxide nanoparticles formed by dewatering the polymerized aluminum oxide still have a rod-like basic structure; the aluminum oxide nanoparticles are stacked into a framework structure in a disordered way, so that the carrier has a large pore volume, a large aperture, a high porosity, a large outer surface orifice and high duct penetrability; and after the surface acidity of the carrier is reduced by the potassium and the phosphorus, the surface activity of a catalyst is reduced, so that asphaltene micelles tend to disperse into the inner part of the carrier to undergo a reaction. Thus, a hydrocracking reaction is restrained, the generation of carbon deposit is prevented, a residual hydrodemetalization reaction is carried out smoothly, and the capability of dissolving metals is improved.