The invention relates to a method for reducing protein of cigar core leaves, in particular to a method for degrading the protein of core leaves by utilizing a protease preparation before the aired core leaves are produced by a formula to improve the quality of the core leaves. In the method, the core leaves which are watered for conditioning are fermented artificially by utilizing a combination preparation of one or more of proteases according to the optimum fermentation parameters, and are subjected to enzyme cutoff to obtain the core leaves of which the quality is improved. In the processedcore leaves, the protein content is reduced, bitter and astringent tastes are reduced, the fragrant and sweet feeling is increased, the irritation is reduced, foreign flavors are removed substantially, and the agreeable aftertaste is improved. The method adopts a simple process, has high repeatability and is low in cost.