The invention relates to a method for preparing scallop hydrolyzed protein powder, in particular to a method for preparing scallop hydrolyzed protein powder by using scallop scrap wastes, which belongs to the field of resource environment. The method uses the fresh or frozen scallop scrap wastes as a raw material and comprises the following steps: firstly, washing the raw material after the scallop scrap waste are washed or unfrozen, mashing into meat paste by a chopper mixer; secondly, grinding the mashed raw material into colloid homogenate by a colloid mill, and processing the homogenate by the ultrasonic waves; and thirdly, adding an exogenous enzyme to be conducted for enzymolysis, filtrating, sterilizing, condensing and drying a hydrolysate to obtain the scallop hydrolyzed protein powder. With the adoption of the ultrasonic waves, the lysate and endoenzyme can be effectively promoted to be released, and the use ratio of the exogenous enzyme can be improved; furthermore, the product has trophism and functionality; and meanwhile, the protein powder is fresh in taste, high in contents of protein and amino nitrogen and implements green and environmental protection, so that the protein powder can be served as an ingredient of the condiments including seafood soy sauce and seafood seasoning packet, and can be served as the raw material for health food and medicine deep processing.