The invention provides a walnut green seedcase black hair dye. The black hair dye comprises a hair dye I and a hair dye II. Due to the combination of the two hair dyes, hair is dyed into black. The walnut green seedcase black hair dye provided by the invention is capable of rapidly dyeing white hair into black, does not contain m-phenylenediamine and other carcinogenic ingredients, also does not contain hydrogen peroxide and other components damaging the hair, and is high in using safety; value development of walnut green seedcases is realized by fully utilizing the walnut green seedcases, anda technical support is provided for development of the black hair dye.