The invention relates to an after-treatment clean process for purifying vat blue 66 dye. The clean process comprises the steps: levigating a vat blue 66 crude product, filtering the levigated vat blue 66 by adopting a 300-mesh
sieve, adding he filtered vat blue 66 in a
sulfuric acid concentrated solution, wherein the weight ratio of the vat blue 66 crude product and the
sulfuric acid concentrated solution is 1: (13-15), and the concentration of the
sulfuric acid concentrated solution is 70 to 75 percent by weight; heating the
mixed solution to 70 to 90 DEG C, stirring and insulating the
mixed solution for 4 to 6 hours, when the vat blue 66 crude product is stirred and insulated in the sulfuric acid concentrated solution, the color of the
mixed solution is turned from dark blue to
olivine, cooling the mixed solution to the temperature of 50 DEG C after the mixed solution is thermally insulated, stirring the mixed solution for 4 to 8 hours, filtering the mixed solution, washing
filter cake by utilizing the70% to 75% sulfuric acid concentrated solution or the sulfuric acid solution which is identical in the concentration, adding water to the
filter cake, pulping the
filter cake, heating the pulp to the temperature of 80 DEG C, preserving the pump for 0.5 to 1 hour, and
drying the filter cake at the temperature of 90 DEG C to obtain a vat blue 66 dye dry product. The sulfuric acid concentrated solution with the concentration of 70 to 75 percent is obtained by after-
processing the sulfuric acid concentrated mother solution obtained by purifying the vat blue 66. The invention provides the after-treatment clean production process of the vat blue 66.