Abstract: Defatted rice bran antioxidant peptide (DRBAP) was produced by hydrolyzing defatted rice bran protein with Alcalase, and was purified with DEAE-52 and SephadexG-15 column chromatograph, then identify its purity through thin-layer chromatogram.Its antioxidant activity was investigated in several experimental systems in vitro such as antioxidant activity in linoleic acid system, free radical scavenging capacity and ferrous ion-chelating effect.The amino acid profile and molecular weight distribution were analysed.The result showed that fraction G4 with higher antioxidant activities was purified.Contrast with unpurified DRBAP, Ferrous ion- chelating effect of G4 improved 11 percent as well as its light absorption value linoleic acid system decreased 0.7, and its scavenging activity of DPPH·, ·OH and O2-· improved 20%, 9%, 16%, respectively.Asp, Glu, Leu, Phe, Arg and Pro were the major constituent amino acids.The molecular weight distribution profile of G4 exhibited that the ratio, with molecular weight low than 1000u and 500u, was 90.83% and 14.38%, respectivily.