The inhibitory effects of four kinds of plant polyphenol containing a catechol structure（caffeic acid， chlorogenic acid， catechin and quercetin） on the activity of lipoxygenase（LOX） were studied using the linoleic acid - LOX system. The underlying mechanisms were studied by Linweaver-Burk plot analysis and fluorescence spectrometry. The LOX inhibitory activities of four kinds of plant polyphenol were in the order of quercetin > catechin > caffeic acid > chlorogenic acid. Caffeic acid and chlorogenic acid were mixed noncompetitive inhibitors of LOX. However， quercetin and catechin were noncompetitive inhibitors of LOX. The quenching constant， binding constant and number of binding sites of the interaction between quercetin / catechin and LOX were greater than those of the interaction between caffeic acid / chlorogenic acid and LOX， indicating that quercetin / catechin may have higher binding affinity towards LOX. LOX had multiple binding sites for four kinds of plant polyphenol. The binding sites of LOX for chlorogenic acid or caffeic acid were located close to tyrosine residues. The binding sites of LOX for catechin had similar average distance towards the tyrosine and tryptophan residues. The binding quercetin was closer to tryptophan than tyrosine residues. Quercetin had synergistic effect with catechin at low concentration， which could effectively inhibit soy protein oxidation through inhibition of LOX.