American Heart Association issued a statement in 1999 which put forward a point of view that “diabetes is a cardiovascular disease”, which made experts in cardiology and endocrinology pay more attention to the relationship between the two diseases. Then, studies on diabetes mellitus and cardiovascular diseases emerged one after another, but there was no consensus finally achieved in their conclusions. Diabetes is a cardiovascular risk factor. About 2/3 diabetic patients died of cardiovascular diseases, and the cardiovascular death of diabetic patients was 2?3 times higher than that of non-diabetic patients. About the relationship between diabetes and coronary heart diseases, there was a great deal of evidence, but the results of the studies were different. In this paper, we reviewed representative clinical trials, and discussed the relationship between diabetes and cardiovascular diseases in 3 aspects, that is, hyperglycemia and cardiovascular events, diabetes as cardiovascular risk equivalents, and diabetes is not a cardiovascular disease.