Abstract: Crude polysaccharide ATB was extracted from the stems of Akebia trifoliate with 5% NaOH. It was then subjected to DEAE-Cellulose column chromatography and purified by Sephadex G-200 chromatography. Finally, a pure polysaccharide ATBB-2 was obtained. The molecular weight of ATBB-2 was estimated to be 2.3×10⁵. By total acid hydrolysis, the analytical results indicated that ATBB-2 is composed of Rha, Ara, Xyl, Gal, Glc and GalA in a molar ratio of 1.22∶1.00∶1.10∶0.85∶0.24∶0.82. Methylation analysis, periodate oxidation analysis, Smith degradation, partial acid hydrolysis, ¹H and ¹³CNMR showed that ATBB-2 is a highly branched molecule without a main chain.