The invention relates to a method for producing an alkali protease. The classification name of bacterial strains is Bacillus alcalophilus, and the preservation number is CGMCC No.5313. According to the fermentation process in the invention, clear liquid fermentation is combined with fed-batch fermentation, a cottonseed cake powder enzymatic hydrolysate is prepared from crude cottonseed cake powder, and a fed-batch carbon nitrogen source fermentation mode is adopted, so the fermentation enzyme activity is effectively improved, the enzyme activity of a 7L fermentation tank, which reaches 41000U/mL, is 13.9% higher than the original enzyme activity of 36000U/mL of the 7L fermentation tank, the late enzyme separation purifying difficulty is reduced, the production cost is reduced, and good economic benefits are obtained.