The invention relates to soybean milk powder for a lamb, prepared from enzymolysis fermented full fat soybean, whole milk powder, whey powder, lactose, fatty powder, lysine, methionine, tryptophan, animmunopotentiator, choline chloride, mountain flour, calcium hydrogen phosphate, table salt, a vitamin premix and a mineral premix. A preparation method of the soybean milk powder comprises full-fatsoybean pretreatment, full-fat soybean pre-digestion, mixing, drying and packaging. The advantages are as follows: 1) the plant-derived enzymolysis fermented whole-fat soybean is adopted as a main fatprotein source, the palatability is good, and phospholipid, sterol and functional small peptide are completely reserved; 2) the digestibility is high, the nutritional level is close to that of breastmilk, the palatability is good, the defect of ewe lactation insufficiency can be effectively overcome, and the disease resistance of the lamb is enhanced; 3) the materials are subjected to colloid mill ultrafine pulverization in advance, the pulverization efficiency is high, and the particle size distribution is narrow. Semi-liquid deep enzymolysis fermentation is adopted, the nutrient digestibility is improved, and a high-quality energy protein source with the peptide content up to 50% or more can be obtained, which is non-polluting, hygienic and clean.