The invention discloses a modificator for high-chromium alloy grinding balls and a preparation method thereof, and relates to the technical field of wear-resistant material modificators. The chemicalcomponents of the modificator for high-chromium alloy grinding balls comprise, by weight percentage, 7-12% of Nb, 5-10% of Ti, 7-13% of Al, 3-8% of Sc, 5-10% of Ce, 15-20% of Si, 2-6% of B and the balance Fe. The preparation method includes the steps that pure aluminum is heated to be molten; then ferro-columbium alloy, ferro-titanium alloy, ferro-boron alloy, aluminum scandium alloy, ferro-ceriumalloy, pure silicon and pure iron are added, and heated to be molten; after all the components are molten, the melt is cast into a metal mold and cooled; and cast ingots are taken out, and the modificator is obtained. The modificator is used for modification of high-chromium alloy grinding balls, molten steel can be purified, grains and structures can be effectively refined, the form and distribution form of carbide are improved, the carbide is dispersed evenly, a substrate is reinforced, good toughness is achieved after heat treatment, abrasion resistance is good, and the service life is prolonged. Besides, on the basis of not affecting the performance of grinding balls, the contents of precious metal elements such as Mo, Ni and Cr are reduced, and the production cost is lowered.