The invention discloses a preparation method of a double-hole-structure alumina supporter. The preparation method comprises the steps of weighing a certain quantity of pseudo-boehmite dry glue powders, evenly mixing the pseudo-boehmite dry glue powder with a certain quantity of peptizing agent and extrusion-auxiliary agent, then adding a certain quantity of ammonium bicarbonate aqueous solution in materials, mixing and nipping obtained materials into a plasticizer, squeezing into stripes and molding, placing molded materials in a sealing container, and roasting to prepare the alumina supporter after hydro-thermal treatment. The temperature of the hydro-thermal treatment is 70-120 DEG C, and the treatment time is 5-10 hours. Roasting is carried out at the temperature of 600-750 DEG C for 2-4 hours. The mass concentration of an ammonium bicarbonate solution is 40%-80%, the adding quantity of the ammonium bicarbonate solution is calculated according to NH<4+> and Al<3+>, and a molar ratio of the NH<4+> to Al<3+> is (0.5-1):1. According to the preparation method, the preparation procedure is simple, the prepared alumina supporter is in double-hole distribution and has good mechanical strength, and the preparation method is suitable to the field of preparation of heavy oil and residual oil hydrodemetallization catalysts and the like.