The invention discloses a method of utilizing fermentation of aquatic product protein and feather meal to prepare growth-promoting small peptide for poultry.The method mainly includes following steps: mincing fresh aquatic product leftovers; adding the minced aquatic product leftovers and hydrolyzed feather meal into an enzymolysis tank, adding nutrient and water, and mixing well to form a fermentation medium; inoculating Bacillus methylotrophicus HL-4 capable of generating keratinase into the enzymolysis tank, and performing enzymolysis and fermentation at the same time; after fermentation is finished, filtering fermentation liquid to remove precipitate to obtain supernate, and subjecting the supernate to concentration and spray drying to obtain the growth-promoting small peptide for poultry.The small peptide prepared by the method is rich in aquatic product protein and keratinase peptide, can remarkably promote growing of poultry and has good application prospect.