The structure of a high molecular weight heteropolysaccharide (60P) isolated from Artemisia sphaerocephala Krasch was elucidated using methylation analysis and 2D NMR spectroscopy. 60P (Mw: 551kDa) was isolated from A. sphaerocephala Krasch (ASK) seeds, using hot water extraction and ammonium sulphate salt precipitation. Methylation and GC–MS analysis indicated that 60P was mainly composed of three types of sugar residues: 4-Xylp (27.8%), 2,4-Xylp (26.0%) and T-GlcpA (22.5%); small amount of 4-GalpA, 4-Glcp, T-Araf, T-Arap and 4, 6-GalpA were also detected with comparable molar ratio. Based on the results of monosaccharide composition, methylation analysis and NMR spectroscopy, a proposed structure is shown below: [Display omitted] R represents one of the following groups: T-Araf, T-Arap, T-Araf→3-Araf (1→ and T-Arap→3-Araf (1→.