Abstract: Most of the traditional permanent hair dyes containing aniline molecules have the risk of carcinogenicity and sensitization. Since polydopamine has a similar molecular structure to eumelanin and good biocompatibility, the use of polydopamine in hair dyeing has become a hot research topic. However, due to the hydrophobic structure of the hair surface, the adhesion of dopamine in situ deposition on the hair surface is weak. Here, by taking advantage of the effect of hyaluronic acid (HA) to hair, dopamine (DA) was grafted onto HA via Schiff base reaction to strengthen the interactions between polydopamine and hair. The chemical structure of DA grafted hyaluronic acid (DAHA) was confirmed by Fourier Transform Infrared Spectrometer (FT-IR), Ultraviolet-Visible (UV-Vis) spectrophotometer, Proton Nuclear Magnetic Resonance (¹H-NMR). The dyeing properties assisted by DAHA were characterized by Scanning Electron Microscope (SEM), single fiber strength tester and colorimeter. Results show that DA has been successfully grafted onto HA, and the grafting ratio for HA with a number average molecular weight of 0.2×10⁴—1.0×10⁴ was 34%. Compared with the hair samples dyeing without DAHA, the hair pretreated with DAHA has better color fastness after 30 washes. Moreover, with DAHA pretreatment, the tensile strength of hair improves, and the improvement rate is about 7.4%. SEM photos demonstrate that the polydopamine nanoparticles on the surface of hair dyed with DAHA were more uniform than those without DAHA.