The invention discloses a preparation method of hydrolyzed vegetable protein. According to the method, vegetable protein is taken as a raw material, 9 to 20 times of water is added, and protease or protease-producing microorganism is added for enzymolysis or fermentation, so as to enable the degree of hydrolysis of the vegetable protein to reach 50 to 60 percent, and obtain hydrolysate containing protease activity; saccharomycetes are inoculated in the hydrolysate containing protease activity, fermentation is performed for 12 to 96h at the temperature of 5 to 30 DEG C, so as to enable the concentration of the saccharomycetes to reach 108 to 109cfu/ml, and obtain yeast fermentation broth; the yeast fermentation broth is heated to 40 to 55 DEG C, and heat preservation is performed for 3 to 6h, so as to obtain crude protein hydrolysate; the crude protein hydrolysate is filtered, concentrated and dried to obtain the hydrolyzed vegetable protein. The hydrolyzed vegetable protein prepared by adopting the method provided by the invention has a rich flavor.