The invention relates to a preparation method of a catalyst for coproducing isopropanol and methyl isobutyl ketone by acetone hydrogenation. The catalyst comprises an alumina carrier and Ni and Mg loaded on the gamma-Al2O3 carrier, and particularly comprises, by total weight, 10-18% of the Ni, 3-8% of the Mg and the balance alumina; and the BET specific surface area of the catalyst ranges from 100m<2> / g to 180m<2> / g, and the pore volume of the catalyst ranges from 0.35mL / g to 0.55mL / g. The preparation method includes steps of (1), preparing the carrier by details of weighing pseudo-boehmite powder, adding binders and extrusion assistants into the pseudo-boehmite powder, forming by strip extrusion or granulating by rotation, drying and calcining, cooling to reduce temperature so as to obtain the stripped or spherical carrier; (2), impregnating the carrier into magnesium nitrate by details of loading a magnesium additive onto the carrier by means of saturated impregnation, drying and then calcining for 2-6 hours at the temperature ranging from 400 DEG C to 500 DEG C; (3), loading the actively metallic nickel by details of impregnating for 10-24 hours and calcining for 2-6 hours at the temperature ranging from 350 DEG C to 480 DEG C; and (4), loading the actively metallic nickel again by details of drying a semi-finished product, impregnating the dried semi-finished product into impregnation liquid of nickel nitrate again, repeating the step (3) once, and calcining the semi-finished product for 2-4 hours at the temperature ranging from 400 DEG C to 450 DEG C so as to obtain the finished catalyst.