The invention discloses macroporous alumina and a preparation method thereof. The macroporous alumina of the invention has the properties that the macroporous alumina is a gamma crystalline state, thetotal porosity is 60%-85%, the macropore diameter is 100 nm-1000 nm, the proportion of macropores to the total porosity is 40%-75%, the macropores are evenly distributed and three-dimensionally penetrated, a ratio of the wall thickness to the pore diameter of the macropores is 0.7-3.0, and the side crushing strength is 8-25 N/mm. The preparation method of the macroporous alumina includes the following steps: (1) preparing aluminum sol; (2) evenly mixing inorganic aluminum salts, polyethylene glycol, the aluminum sol obtained in the step (1), organic compounds containing amide groups and a low-carbon alcohol aqueous solution; (3) adding epoxypropane and/or pyridine into the mixture obtained in the step (2), evenly mixing the mixture to obtain gel, and carrying out aging to obtain an agingproduct; and (4) immersing the aging product by using the low-carbon alcohol aqueous solution, carrying out solid-liquid separation, and drying and roasting a solid phase to obtain the macroporous alumina.