The invention, pertaining to a field of food brewing technology, particularly relates to a kidney bean sauce and a brewing method thereof. According to the invention, white kidney beans are used as the main raw material, flour and preserved fruit syrup are used as auxiliary materials, a plurality of strains such as aspergillus oryzae, aspergillus niger, lactic acid bacteria, yeast and the like are used as fermentation microorganisms, and the product is obtained after three stages of temperature-controlled fermentation, that is, flavor-generating fresh fermentation, chromophore-generating fermentation, and aroma-generating fermentation. The method of the invention, by adopting a band temperature-controlled method, controls growth of the aspergillus, maintains high activity and quantity of the protease, carries out enzymolysis on the kidney bean protein, and produces large amounts of amino acid and peptide. By using the lactic acid bacteria and the yeast for fermentation, and an insulation reaction, the final product has unique and rich sauce flavor and color. The sauce of the invention tastes fresh and delicious, has a total ammonia nitrogen content of 1.64% which increases by 26% compared with that of traditional methods, and has abundant volatile flavor substance.