The invention discloses a preparation method of a black waterborne
polyurethane dye based on black chromophores in diols. The preparation method is characterized by comprising the following steps of enabling activated
hydrogen in amino groups or hydroxyls contained in molecular structures of three black dyes to react with chloroethanol to obtain three black diols; then, combining the black diols with micromolecular diols, and partially or completely substituting the micromolecular diols; and next, reacting with diisocyanate, macromolecular diols and a hydrophilic chain
extender to obtain the black waterborne
polyurethane dye. By using the method, other micromolecular chain extenders can be partially or completely substituted with the black diols, so that
solid content of an
emulsion is wide in distribution range and adjustable, and the content of the black chromophores in a molecular chain of
polyurethane can be controlled as required; and meanwhile, the black chromophores enter the molecular chain of the dye in a chemical bonding way, so that the characteristics of high
temperature resistance,
solvent resistance and migration resistance of a macromolecular dye can be sufficiently exerted, and the dye is good in durability, high in color fastness and good in safety.