Compared with acid-base hydrolysis, protease hydrolysis has the advantages of mild conditions and no residual harmful substances. The commonly used protease preparations in fermented soybean meal are neutral protease and acid protease. Neutral protease works better in poultry, and acid protease works better in mammals. Protease preparations must be used in conjunction with lactic acid bacteria (yeast, etc.). After the soy protein is hydrolyzed by protease, some peptide bonds are broken, destroying the structure of antigenic determinants, and forming small molecules with no immunological activity, thereby changing the original immunity of the protein Activity, degradation degree is about 40%~45%. When the degree of hydrolysis reaches more than 25%, the antigenic determinant will lose its original antigen structure and immune activity. The specific application of protease preparations in fermented soybean meal can effectively improve the utilization rate of soybean meal protein and reduce feeding costs.