The link between diabetes and coronary heart disease has aroused widespread interest among endocrinologists and cardiovascular physicians. In 1999, the American Heart Association (AHA) proposed that “diabetes is a cardiovascular disease”, and in 2001, the third guideline of the Adult Cholesterol Education Program of the United States proposed that diabetes is an “equivocal risk” for coronary heart disease. “Since then, the communication between endocrinologists and cardiologists has become closer. Numerous epidemiologic studies have shown that diabetes mellitus or abnormal glucose tolerance is an independent risk factor for cardiovascular disease. The incidence of acute myocardial infarction in diabetic patients with coronary artery disease is one times higher than that in nondiabetic patients with coronary artery disease. 3.The risk of cardiovascular disease in diabetic patients is 2-4 times that of non-diabetic patients. 4, in diabetic patients, 50%-60% die of coronary heart disease. The reason for the increased incidence of coronary heart disease in diabetic patients is not very clear, and it is currently believed that hyperglycemia, obesity, hypertension, dyslipidemia, hyperfibrinogenemia, hyperinsulinemia, oxidative stress and so on can lead to endothelial cell damage, smooth muscle cell dysfunction, platelet function and coagulation abnormality, lipid deposition, and ultimately the formation of atherosclerosis plaque protruding into the lumen, so that luminal narrowing, blood flow is impeded, resulting in Myocardial ischemia and hypoxia. Coronary heart disease combined with diabetes mellitus patients compared with non-diabetic patients: coronary atheromatous lesions are more serious, extensive and complex, often dominated by small vessels and long lesions, with significantly narrow lumen; there are often diffuse lesions, multi-branching lesions, distal lesions, small-vessel lesions, left main stem lesions, bifurcation lesions, and poor collateral circulation and other lesion characteristics; myocardial infarction of the anterior wall and multiple infarctions and large infarctions are more common, and the mortality rate is high. Because diabetic patients are often combined with neuropathy, pain sensation is slow, more than one-third of the patients do not have typical angina manifestations, and even “painless” infarction occurs, which is easy to mislead the condition. Therefore, when the patient appears the following symptoms should be alert to whether angina pectoris, myocardial infarction attack, should go to the hospital as soon as possible. These symptoms include: 1, breathlessness, shortness of breath, etc.. 2, missed heartbeats, irregular heartbeats, etc. 3.Presentation of pain in areas other than the chest, such as headache, toothache, sore throat, shoulder pain, back pain, arm pain. 4.Abdominal discomfort, abdominal pain, nausea and vomiting and other symptoms. 5, dizziness, transient loss of consciousness, convulsions and so on. However, blood sugar control is not the lower the better, hypoglycemia brings great harm, can induce angina pectoris, acute infarction, sometimes even fatal. Therefore, for most patients with diabetes mellitus combined with coronary artery disease, the glycemic control target should be looser than that of general diabetes mellitus patients, and endocrine specialists should set appropriate glycemic control targets for the patients.