The invention relates to an aqueous enzymatic method for preparing protein peptide powder from soybean hydrolysate and belongs to the technical field of soybean product processing. The method comprises the steps as follows: (1) soybeans are peeled and crushed, extrusion treatment is performed, and an extruded product is obtained; (2) water is injected into an enzymatic hydrolysis reaction tank, steam heating is performed, the extruded product is added, a mixed solution is obtained, the pH value of the mixed solution is adjusted, and alkaline protease is added for enzymolysis; (3) centrifugal separation is performed with a horizontal centrifuge after enzymolysis, and emulsified oil, a hydrolysate I and residues I are obtained; (4) isolated soy protein is added to the hydrolysate I, the pH value is adjusted, pepsin is added for enzymolysis, centrifugal separation is performed after enzymolysis, soybean oil, a hydrolysate II and residues II are obtained, alkali is added to the hydrolysate II for neutralization until the pH is neutral, and desalination is performed with an ultrafiltration membrane; (5) malt syrup, maltodextrin and other auxiliary materials are added to desalinated hydrolysate for blending, uniform mixing is performed, a protein emulsion is formed, homogenization, vacuum concentration and spray drying are performed, and protein peptide powder is obtained. The method adopts a simple process and is low in cost, the prepared protein peptide powder has high nutritional value, has strong milk aroma, tastes fine and has good digestibility, besides, the instant solubility of the protein peptide powder is significantly improved, and the protein peptide powder is suitable for industrial continuous production.