The invention relates to a grain-saving feed diluted enzyme additive and a preparation method thereof. The grain-saving feed diluted enzyme additive consists of rare earth chloride, rare earth nitrate, lignin enzyme, cellulase, hemicellulase, complex enzyme, medical stone, bentonite, talcum powder, zeolite, ferrous sulfate, manganese sulfate, zinc sulfate, copper sulfate, cobalt sulfate, calcium sulfate and sodium selenite. Lanthanide series light rare earth and enzyme are taken as main materials, Chinese medical stone is taken as a carrier, a proper amount of microelements is taken as feed additive, catalysis of the rare earth, degradation of the enzyme and nutrition functions of the microelements are combined according to optimal proportion. The feed made from the additive has rich nutrition, delicious flavor and high digestivity, and can increase yield factor of livestock and poultry by 6-8%, save 10-12% feed, reduce feed cost by 8-10%, and effectively improve product quality.