The invention discloses a method for recovering precious metal from a waste aluminum-based catalyst and preparing high-purity alumina. The method mainly comprises the processes of: roasting, leaching to remove aluminum by using dilute sulfuric acid, recovering the precious metal from slag from which the aluminum is removed by an aqueous solution chlorination method, adding ammonia water into leachate to precipitate an ammonium aluminum sulfate coarse crystal, recrystallizing, and calcining and decomposing to prepare the high-purity alumina. The method specifically comprises the following steps of: mixing the finely ground waste aluminum-based catalyst (40mu m) and ammonium sulfate in a weight ratio of 1:(1.3-1.5), roasting at the temperature of between 300 and 500 DEG C for 2 to 4 hours, performing fluidization leaching on a roasting product by using 1mol/L dilute sulfuric acid for 2 hours, performing solid-liquid separation, and recovering the precious metal from the slag from which the aluminum is removed by the traditional aqueous solution chlorination method, wherein the recovery rate of the precious metal is over 99 percent; and adding the ammonia water into the leachate to regulate the pH value and precipitate the ammonium aluminum sulfate coarse crystal, recrystallizing, and calcining and decomposing to prepare the high-purity alumina, wherein the purity is over 99.99 percent, and the recovery rate is over 95 percent. The invention has the advantages that: the process is reasonable, the method is easy to operate, the added value of a product is high, pollution is light, mass production is convenient to implement, and the like.