Abstract: To investigate the antioxidant activities in vitro of different polarity fractions of 75% ethanol extract from Mappianthus iodioides,five polarities of extracts were obtained by using different polarity solvents,such as petroleum,chloroform,ethyl acetate,normal butyl alcohol and water. The content of flavonoids was detected by absorption spectroscopy. Their antioxidant activities were evaluated by reduction energy capability and scavenging capability of DPPH,hydroxyl free radical and superoxide anion free radical. The results showed that all of the extracts had strong deoxidization ability of Fe3+. Ethyl acetate extracts had significant deoxidization ability. All the different polarity fractions of extract antioxidant activities were observed,of which the ethyl acetate extract had highest antioxidant activity,and 50% inhibitory concentration(IC50) of DPPH of the ethyl acetate extract was 0.28mg/m L,50% inhibitory concentration(IC50) of ·OH of the ethyl acetate extract was0.41mg/m L. When the concentration of the ethyl acetate extract reached to 0.2mg/m L,O2-· scavenging rate was 42.88%. In addition,total flavonoids content of ethyl acetate extract was significantly higher than that of others,reached to 609.96mg/g,which might related with its higher antioxidant activity. It was indicated that ethyl acetate extract of 75% ethanol extract from Mappianthus iodioides had good development potential for natural antioxidant.