The optimized serine alkaline protease (SAP) gene was cloned into expression vector pYES2 and expressed in Saccharomyces cerevisiae Whu2d. The S. cerevisiae engineering bacteria was used to study the enzymatic properties of recombinant alkaline protease and the effect of degrading protein anti-nutritional factors in soybean meal. The results indicated that the activity of alkaline protease in the fermentation broth of recombinant S. cerevisiae was 55.2% higher than that of the original strain. The optimum reaction temperature and pH were 45 ℃ and 8 respectively, and the stability was good at pH 7-10.5, where the relative enzyme activity could be maintained above 80%. Compared with the original strain, the content of acid soluble protein in soybean meal increased by 42.1% and the content of crude protein and β-conglycinin had no significant difference. The contents of glycinin and trypsin inhibitor were reduced by 41.9% and 57.4%. The results showed that the S. cerevisiae engineering bacteria could be used for the processing of feed, food and other protein-rich materials.