The lipid peroxidation of myocardial mitochondria induced by lipoxygenase and lipid radicals, and the inhibitory effects of ( -- )-epigallocatechin gallate [( -- )-EGCG] were studied by using the electron spin-trapping resonance technique. The results showed that 4-POBN could trap free radicals produced by lipoxygenase in myocardial mitochondria and got a ESR spectrum including six lines and four lines peaks. ( -- )-EGCG had no effect on the activity of lipoxygenase, but scavenged the lipid radicals of the system and showed dose-efficiency relationship. In addition, ( -- )-EGCG could inhibit lipid peroxidation, but, the inhibitory effects did not change with the increasing concentrations of ( -- )-EGCG used among in our experiment. The inhibitory ratio was about 21%.