The invention discloses a composite nutritional muscle strengthening powder having a muscle building function and a preparation method thereof. The muscle strengthening powder is composed of: proteinpowder, creatine, panax-notoginseng, codonopsis pilosula, kudzu root powder, acanthopanax root, American ginseng, mint oil, microcrystalline cellulose, roselle extract, chrysanthemum flower extract, coix seed powder, fructus momordicae extract, green tea powder, lotus leaf powder, sea salt, juice powder, lotus root powder, modified starch, peach flower powder, oat meal, buckwheat, quinoa flour, konjac powder, a stevioside extract liquid, Maca powder, and a microelement supplement. The raw materials are mixed and fully stirred according to weight part ratio, and then the mixture is dried and sterilized to obtain a finish product. In the invention, by proportioning the protein powder, vitamin B groups, vitamin A, vitamin C, vitamin E, Zn and Fe, the muscle strengthening powder can greatly reduce the possibility of various discomfort symptoms during muscle building and has effective improvement effect on growth of muscle, and can effectively inhibit of discomfort generated from stress reaction after fitness.