The invention discloses nutritious composite powder and a preparation method thereof. The nutritious composite powder is prepared from isolated soybean proteins, polydextrose, phospholipid, acerola cherry fruit powder, wheat oligopeptide, a black bean husk extract, inulin, a phaseolus angularis extract, insoluble soybean dietary fibers, corn fibers, an agaricus blazei murill extract, a citrus extract, xylo-oligosaccharide, yam powder, tremella powder, hericium erinaceus powder, agrocybe cylindracea powder, tea polyphenol, vitamin B1, vitamin B2, vitamin B6, pantothenic acid, nicotinic acid, vitamin B12, vitamin C, vitamin A, vitamin D, vitamin E, biotin, folic acid, calcium, magnesium, iron, zinc, selenium, chromium, copper, manganese, sodium carboxymethyl cellulose, edible essence and sucralose. The nutritious composite powder can alleviate and solve the problems of intestinal environment damage and intestinal injury which are caused by simple nutritional ketone production or nutritional unbalance in a conditioning process.