The invention discloses a preparation method for low-molecular-weight fish 
hydrolyzed protein powder. The preparation method comprises following steps of: by taking fresh and alive freshwater fishes as raw materials, and preparing the low-molecular-weight fish 
hydrolyzed protein powder via the processes of 
raw material pre-treatment, deodorization, enzymolysis, 
enzyme deactivation, 
centrifugation, 
desalination, concentration, and 
spray drying. The fish 
hydrolyzed protein powder prepared by the preparation method disclosed by the invention is low in molecular weight, the content of the fish hydrolyzed 
protein powder having a molecular weight of less than 1000 Da achieves more than 80%, and the fish hydrolyzed 
protein powder is easy to digestively absorb; the 
solubility achieves more than 95%; the fish hydrolyzed 
protein powder prepared by the preparation method disclosed by the invention is produced from the freshwater fishes, and rich in source; the preparation method disclosed by the invention provides a new 
route for high-valued utilization for the freshwater fishes; the preparation method disclosed by the invention utilizes a biological enzymolysis technology, as well as is high in efficiency and 
pollution-free; the product is safe, effective, and without toxic and side effects; the low-molecular-weight fish hydrolyzed protein powder is easier to be digestively absorbed than fish protein, capable of being applied to 
infant nutrition formulation foods, convenient foods, instant drinks, seasonings and the like as a food 
raw material or an auxiliary material, and wide in market prospect.