Abstract: 1, 2, 3, 5, 6, 7-hexahydroxy-9, 10-anthraquinone was synthesized by Friedel-Crafts acylation reaction using gallic acid as raw material and methanesulfonic acid as catalyst. The structure of the target product was verified by ultraviolet-visible(UV-vis) spectroscopy, Fourier transform infrared(FT-IR) spectroscopy, nuclear magnetic resonance(NMR) spectroscopy, and liquid chromatography-mass spectrometry(LC-MS) spectroscopy. The antioxidant activities in vitro of hexahydroxy-anthraquinone were evaluated in terms of its scavenging abilities on ABTS radical (ABTS⁺), DPPH radical(DPPH) and superoxide anion radical (O₂^-). The results showed that the molar absorbance coefficient(ε_λmax) of 1, 2, 3, 5, 6, 7-hexahydroxy-9, 10-anthraquinone at the maximum absorption wavelength of 293 nm was 3.25×10⁴ L/(cmmol), which was two times higher than that of the commonly used UV absorber 4-methoxycinnamic acid-2-ethylhexyl ester(OMC), indicating that it was an excellent UV absorber in UVB band. The half-inhibitory concentrations(IC₅₀) of hexahydroxy-anthraquinone for the scavenging of ABTS⁺, DPPH, and O₂^- were 42.1, 39.4, and 30.8 μmol/L, respectively. The scavenging ability of it on ABTS⁺ and DPPH was stronger than that of Vc, but weaker than that of gallic acid, and the scavenging ability of it on O₂^- was stronger than those of Vc and gallic acid.