The invention relates to a hydrotreating catalyst for residual oil and a preparation method for the hydrotreating catalyst for residual oil. According to the catalyst disclosed by the invention, the pore volume is 0.2mL/g to 1.2mL/g; the specific surface area is 40m<2>/g to 200m<2>/g; the average pore diameter gradually increases from centers to outside surfaces along radial directions of carrier particles, and the average pore diameter of parts from the centers of the particles to 50% of particle sizes is smaller than that of parts from 80% of particle sizes to the surfaces by 3nm to 10nm; and aluminum oxide serves as a carrier, and the catalyst contains 4% to 12% of molybdenum and/or tungsten and 0.4% to 4% of oxides of cobalt and/or nickel based on the total weight of the catalyst. The method disclosed by the invention comprises the steps: treating a shaped and pre-calcined aluminum oxide precursor with acidic solutions with gradual-improved concentration; and subjecting the carrier to metal impregnating, then, carrying out predrying and water washing treatment, and finally, carrying out drying and calcination, thereby obtaining the catalyst. The catalyst provided by the invention has high impurity removal activity and stability.