Type　2　diabetes　mellitus　(T2DM)　is　a　risk　factor　for　heart　disease.　However,　the　mechanisms　of　T2DM　involvement　in　cardiac　complications　are　still　unclear.　In　the　present　study,　we　investigated　mitochondria-related　mechanisms　underlying　the　pathogenesis　of　myocardial　disorders　in　diabetic　Goto-Kakizaki　(GK)　rats.　We　found　that　remarkable　myocardial　mitochondrial　deficiency　and　dysfunction　as　well　as　oxidative　stress　occurred　in　the　heart　of　GK　rats.　In　addition,　our　results　suggested　that　the　loss　of　mitochondria　was　in　response　to　elevated　autophagy　and　upstream　FoxO　factors　in　diabetic　myocardium.　More　importantly,　(-)-epigallocatechin-3-gallate　(EGCG),　a　polyphenol　derived　from　green　tea,　successfully　improved　mitochondrial　function　and　autophagy　in　the　heart　of　GK　rats.　Our　findings　revealed　that　diabetes-associated　myocardial　mitochondrial　deficiency　and　dysfunction　was　associated　with　enhanced　autophagy　in　myocardium,　and　EGCG　might　be　a　potential　agent　in　preventing　and　treating　myocardial　disorders　involved　in　diabetes.