Cardiomyocytes hypoxia resulting from ischemia is a major pathological factor in ischemic heart disease(IHD), and diabetes is one of the most common complications in IHD. myocardial damages aggravate and prognosis is worse in patients with coronary heart disease and diabetes, which is probably concerned with the reduction of hypoxia-inducible factor 1 (HIF-1) expression. But the mechanisms of HIF-1 signal transduction system in diabetes are not clear. In recent years, many studies have indicated that increasing expression and activity of HIF-1α in IHD can promote neovascularization and cardiomyocytes survival, decrease ischemical reperfusion injury and myocardial infarction (MI) size, and increase myocardial function. Therefore regulating expression and activity of HIF-1α becomes a new way to treat IHD. Myocardial infarction models were made in GK diabetes rats through the ligation of left anterior descending coronary artery (LADCA). By using immunohistochemistry staining and RT-PCR methods, results suggested that HIF-1α expression decreased and myocardial infarction size increased in GK diabetes rats combined with MI. When treated with cobalt chloride(CoCl₂), blood glucose level decreased, HIF-1α expression increased and myocardial infarction size reduced in GK diabetes rats, which may provide a new insight on treatment of coronary heart disease combined with diabetes by regulating HIF-1 signal transduction system.