Abstract: The brown pigment from Castanea mollissima Blume was a kind of important natural food pigment. In purpose of providing references for the deep application of the brown pigment,in this study,the spectral characteristics,antioxidant activity,chemical composition were studied. The brown pigment of Castanea mollissima Blume was extracted by dissolving in alkaline solution and precipitating in acid solution. The UV and IR were used to determine the spectral characteristic of the brown pigment. Folin-Ciocalteu,phenol-sulfuric acid method and bicinchoninic acid method(BCA)were used to determine the total phenol,polysaccharide and protein content. The ability of scavenging DPPH free radical was used to evaluate the antioxidant activity of the brown pigment. The liquid chromatography was used to isolate compounds from the pigment,and liquid chromatography combined with mass spectrum and nuclear magnetic resonance were used to identify the structures of compounds. The results showed that,the wavelength of maximum absorption peak was 276 nm of the brown pigment water solution. The infrared spectrogram demonstrated typical phenol characteristic. The total phenol,polysaccharide and protein content in the brown pigment were 42.35%,13.75% and 8.08%,respectively. The brown pigment of Castanea mollissima Blume features with strong antioxidant activity,the IC₅₀ of DPPH free radical was 0.44 mg/mL. After separation,10 phenol compounds were obtained,namely,resorcinol(1),2-hydroxy-3',4'-dihydroxyacetophenone(2),catechol(3),protocatechualdehyde(4),3,4,4-trihydroxy-benzoic acid methyl ester(5),2,5-dihydroxyacetophenone(6),β-hydroxypropiovanillone(7),protocatachuic acid methy ester(8),2-propenoic acid(9),ferulic acid(10).