Abstract: AIMTo study the chemical structure of SC3, an acidic polysaccharide from Salvia chinensis. METHODSBased on chemical (including sugar composition analysis, methylation analysis, uronic acid reduction and partial acid hydrolysis) and spectral analysis (IR, NMR, ESI-MS), the structural characterization of SC3 was investigated. RESULTSSC3 was composed Rha, Ara, Gal and GalA, with its mean molecular weight of 7.7×10⁴. By means of methylation analysis, partial acid hydrolysis, NMR and ESI-MS spectrum, the linkages and sequence information of SC3 were obtained. CONCLUSIONSC3 is an complicated acidic polysaccharide, obtained for the first time from the plant.