The invention discloses a lamb milk replacer and a preparation method thereof, and relates to the technical field of lamb milk replacers, the lamb milk replacer comprises a component A, a component B and a component C, the component A is prepared from the following raw material components: puffed corn flour, wheat flour, puffed rice flour, fermented soybean meal, soybean protein isolate, puffed soybeans, skim milk powder, whey powder, glucose, puffed corn type soybean phospholipid oil powder, fat powder, DL-methionine hydrochloride, L-threonine and monocalcium phosphate; the component B is prepared from the following raw material components: multi-mineral No.1 and multi-vitamin No.1; the component C is prepared from the following raw material components: mannofructose, benzoic acid, 50% coated zinc oxide, sodium bicarbonate, a compound enzyme preparation, acid protease, a flavoring agent, L-tryptophan, choline chloride, sodium chloride, neutral protease, yeast powder, a solid mildew preventive, a mycotoxin adsorbent, a sweetening agent, frankincense spice and clostridium butyricum.