Endothelial cells are one kind of the epithelial cells that widely adhere to the lumen of the heart, blood vessels, and lymphatic vessels. They are involved in important processes such as hemostasis, regulation of blood vessels, and angiogenesis in human physiological homeostasis. In addition, recent studies have found that endothelial cells contribute to the pathological progress of various cardiovascular diseases and also have unique capability of multi-directional differentiation. Endothelial-mesenchymal transition is closely related to myocardial fibrosis. This article focuses on vascular endothelial cells, mainly exploring their physiological characteristics and their role in ischemic heart disease and heart failure with a view to providing new ideas for the treatment of cardiovascular disease.