The invention relates to the technical field of catalysts, and provides a preparation method of a modified alumina carrier. The method comprises the following steps: preparing alumina colloid; evenlymixing the alumina colloid with silica sol to form a spherical carrier; and successively performing aging, drying and roasting on the spherical carrier to obtain the modified alumina carrier. According to the method, pseudo-boehmite does not need to be prepared, the aluminum source can be directly formed after gelling, filtration and acid dissolution, the production technological process is greatly shortened, the equipment cost is reduced, and the industrialized production is convenient. The prepared carrier has the advantages of many acidic active sites, large pore size, high strength and large specific surface area. The invention provides a palladium catalyst containing the above carrier and a preparation method thereof. According to the method, the reduction process of a metal does notneed high temperature roasting and hydrogen reduction treatment, the method has the advantages of safety, high efficiency and low energy consumption. The prepared catalyst has the advantages of smallparticle size of palladium nanoparticles, large specific surface area, moderate pore size and high hydrogenation efficiency and selectivity.