5, 6-dihydroxyindole, an important intermediate of melanogen, was first found in nature in a plant. Permanent hair dyes with non-toxic and side effects are gradually replacing aniline compounds as the best choice for synthetic hair dyes. As a permanent hair dye, 5, 6-dihydroxyindole has the same hair dyeing mechanism as p-phenylenediamine and its derivatives. It acts on the keratin fibers of hair, making the dyeing effect very obvious. It enters the interior of the hair pulp, and is not easy to fade after dyeing, nor is it greatly affected by sunlight. For a long time, the effective blackening ingredient in hair dye is p-phenylenediamine and its derivatives, which have carcinogenic, teratogenic and allergic effects on the human body, affecting the health of users. As an effective substitute, 5, 6-dihydroxyindole is produced by the organism itself, which is non-toxic to the body and has side effects.