Peroxyl radical derived from thermal decomposition of 2,2'-azobis ( 2-amidinopropane ) dihydroehloride ( AAPH ) under aerobic condition was selected as representatives of lipoxygenase-mediated lipid peroxidation derived free radicals in the paper, and effect of oxidative modification by peroxyl radical on functional properties of soy protein was studied. The results indicated that as concentration of AAPH increased, protein carbonyl content, water holding capacity, and oil holding capacity of soy protein increased, solubility of soy protei...