The invention discloses a method for preparing a hydro-demetalization catalyst for heavy oil. The method comprises the following steps of: firstly, preparing an alumina carrier, then, loading active metal components by using an immersion method, and obtaining the final hydro-demetalization catalyst after drying and roasting, wherein the process for preparing the alumina carrier comprises the following steps of: (1) evenly mixing pseudoboehmite dry colloidal powder with an extrusion aid, and then, adding an aqueous solution in which a physical pore-expanding agent and a chemical pore-expandingagent are dissolved, wherein the physical pore-expanding agent is a carbohydrate, and the chemical pore-expanding agent is phosphoric acid, phosphate or borate; (2) evenly mixing the materials prepared in the step (1), and then, forming; and (3) drying and roasting the materials prepared in the step (2) so as to prepare the alumina carrier. The hydro-demetalization catalyst for the heavy oil, prepared by the method disclosed by the invention, has the advantages of larger pore volume, larger pore diameter, concentrated pore distribution, good mechanical strength, and higher activity and higheractivity stability in the process of the hydro-demetalization for the heavy oil.