The invention discloses a fresh water fish hydrolyzed protein powder and a preparation method thereof. The preparation method comprises the following steps: (1) cleaning processed fish bodies, and cutting the fish flesh into fish blocks with uniform size by using a fish block machine; (2) weighing ginger and shallots, putting the ginger and shallots into drinking water, boiling, putting the ready-made fish blocks, and boiling for 2 minutes; (3) taking the ginger and shallots out, and pulverizing and homogenizing after the fish-water mixture is cooled to room temperature, thereby obtaining minced fish; (4) adding animal protein hydrolase and flavoring proteinase into the minced fish for hydrolysis; (5) inactivating enzymes for 15 minutes, adding 30g of active dry yeast into every 1L of hydrolysate, and fermenting for 2 hours while keeping the temperature; and (6) concentrating the obtained hydrolysate, and carrying out spray drying to obtain the hydrolyzed protein powder. The invention is simple to operate and convenient for industrialized production, and has the advantage of low cost; and the product can be easily dissolved in water, does not have fishy smell or bitter taste, and has a unique flavor.