Abstract: The Minimum Inhibitory Concentration (MIC) of 9 compounds obtained from Polygonum posumbu for the first time was evaluated by microdilution method on 96-well plates against for 4 bacterial strains and 7 fungal strains.The results showed that β-sitosterol (1), β-sitosterol-3-O-β-D-glucoside (2), gallic acid (3), quercetin-3-O-(2″-O-galloyl)-β-D-glucopyran-oside (4), quercetin-3-O-β-D-glucopyranoside (5), quercetin (6), inositol (7), succinic acid (8), and n-butyl-β-D-fructopyranoside (9) had different inhibitory effect to these strains.Among them, flavonoids 4, 5 and 6 had a good inhibitory effect on bacteria and fungus.In addition, the antioxidant activity of selected compounds was studied, and the free radical scavenging rate was determined by DPPH method with Vc as the positive control.The antioxidant activity result was that 4 > 3 > 6 > 5 > 9 > 1 > 2.The antioxidant capacities of compounds 3, 4 and 6 were better than that of Vc.Combined with the structures of these compounds, it comes to a conclusion that the compounds containing O-diphenolic hydroxyl structure have a certain antioxidant capacity, and the more o-diphenolic hydroxyl, the stronger antioxidant capacity.