Abstract: AIM　To study the structure and antioxidative activity of polysaccharide from Asparagus cochinchinensis. METHODS AND RESULTS　the tube roots of Asparagus cochinchinensis was extracted with boiling water. From the extract, a polysaccharide, ACP₁ was separated using DEAE-cellulose and purified by Sephadex G-150 column chromatography. Its structure was studied by composition analysis, IR, periodate oxidation analysis, Smith degradation, CrO₃ oxidation, methylation analysis, ¹H and ¹³CNMR analysis etc. ACP₁ was found to be composed of Gal and Glc, in the ratio of 1.00∶0.87, with the molecular weight of 10.4×10⁴ and ［α］15D=+64(c 0.54, H2O). ACP₁ contained a backbone composed of 8β-(1→4) linked D-galactopyranosidic and 6α-(1→6) linked D-glucopyranosidic linkages, a glucosyl branch is attached to 3-O of a galactosyl residues of the main chain. The superoxide anion() produced by NBT-PMS-NADH system was scavenged and the lipid peroxidation induced by Fe²⁺-ascorbic acid in mouse liver microsome was inhibited, the hemolysis of rat RBC induced by H₂O₂ was antagonized. CONCLUSION　ACP₁ is a galacto-glucan and has distinctive effect of antioxidation.