Abstract: The antiperoxidant activity of glycyrrhiza flavonoid (F G) was studied by using colorimetric estimation of lipid peroxide(MDA) formation. The scavenging effects of FG on O₂- and OH^- was investigated by using chemiluminescence method and spin trapping technique in different systems. The results were as follows. FG 2.8～25μg/ml effectively inhibited MDA formation induced by incubating mice liver homogenateat 37℃ for 1h; FG 0.265～26.5μtg/ml or 2.58～258μg/ml was shown to markedly scavenge O₂ in alkaline/DMSO or xanthine/xanthine oxidase systems, respectively.in a concentration-dependent manner. FG 144μg/ml or 258μg/ml also significantly scavenged the active oxygen radicals produced by PMN stimulation with PMA or OH^- produced in Fenton's reaction respectively. The results suggest that FG may be used as an antioxidant.