Abstract: The polysaccharides from Sepia esculenta ink are potential candidates for biomedical applications due to their functional properties. In our study, a heteropolysaccharide, SE-1, isolated from Sepia esculenta ink, had a molecular weight of 13.1 kDa and a monosaccharide composition of Man:GlcN:GlcUA:GalN:Xyl:Fuc=1.00:1.38:0.65:2.89:0.76:1.99. Through partial acid hydrolysis, methylation and one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) spectroscopic analyses, it is indicated that the structure of SE-1 consists of →4)-α-D-GlcpNAc-(1→, →4)-α-L-Fucp-(1→, →3)-α-D-GalpNAc-(1→, →2,6)-α-D-Manp-(1→ and →3)-β-D-GlcpUA-(1→ as the main chain and single terminal β-D-Xylp-(1→, which links to O-2 of (1→2,6)-α-Manp, as the side chain. A new aminosugar-abundant heteropolysaccharide was isolated from S. esculenta ink for the first time.