The invention provides an aluminum oxide based hydrorefining catalyst as well as a preparation method and application thereof. The method comprises the following steps: 1, immersing active metal components into an aluminum oxide carrier, and drying and roasting to obtain an active metal component loaded catalyst; and 2, introducing an organic complexing agent into the active metal component loaded catalyst and drying to obtain the aluminum oxide based hydrorefining catalyst, wherein the aluminum oxide carrier comprises delta-Al2O3 or theta-Al2O3. The aluminum oxide based hydrorefining catalyst provided by the invention can be used for FCC diesel oil so that the yield of the FCC diesel oil is higher than 99%, the content of sulfur is lower than 10ppm, and China 5 standard requirements are met.