Abstract: The nutritional components, the content and composition of the polyphenolics in the tuber of Pachyrrhizus erosus L.from Yunnan province was investigated, and the antioxidant activities of the polyphenolics were determined.The results showed that the tuber of Pachyrrhizus erosus L.had a high-level of soluble carbohydrate and starch, a significant amount of ascorbic acid, niacin and pyridoxine, being 11.55, 0.166 and 0.207mg·100g-1 fresh weight (FW) , respectively.The polyphenolic content in tuber was 2.06mg·g-1dry weight (DW) .Gallic acid, vanillic acid, caffeic acid and rutin were the dominate components, being 0.55, 0.27, 0.12 and 0.15mg /g DW, respectively.The polyphenolic extracts showed significant reducing power, DPPH-scavenging activity, OH-scavenging activity and lipid peroxidation inhibition ability, with EC 50 and IC 50 being 1.33μg·mL-1, 4.15, 7.70 and 17.00μg·mL-1respectively.