The fish scale polypeptide has an inhibitory activity on angiotensin converting enzyme. Therefore, it is a very important means to recover the fish scale by decalcifying the fish scale and preparing a certain active polypeptide by enzymatic hydrolysis. However, a large amount of inorganic salts remain in the enzymatic hydrolysis process, which affects the activity. Therefore, more and more researchers are beginning to use adsorption resin treatment as the first step in the separation and purification of enzyme products.