Abstract: Genistein was the main component of i soflavone in the fermented soybean f ood.The immune antigen of BSA -genistein andthe coatedantigenof OA -genistein were synthesizedr espectively,andidentified with ul traviolet absorptionspectrometryandSDS -polyacrylamidegelelectrophoresis.TheantibodyIgGofantigenisteinwa spuredwith saturatedsolutionof(NH 4 ) 2 SO 4 andthe columnchromatography ofSep hadex G -25,with1:1600titer ofanti body IgG of antigenistein.The competitive ELISAfor detecting the genistein con tent in the fermented soybean food wa s devel-oped,with6.25～150μg /Lofthedetectingconcentrationr angeofgenistein,therecoveryof87%～102%,theaffinity constant of 1.62×10 8 ,and the 9.8%and 4.57%cross reactio n ratios of antibody for daidzin and f ormononetin re-spectively,while no cross reaction for catechin,tannin,quercetin and riboflavin was observed.The ELISAmethodand thin -leaver chromatography method were also compared for the effect of assaying genistein.

Key words: Genistein , Enzyme -linkedimmunosorbent assay , The fermented soybeanfood