Vascular endothelial cells form a thin layer of flattened cells that cover the surface of the vessel wall, As an effector tissue, the vessel wall responds to various stimuli to release vasoactive substances to maintain homeostasis. However, endothelial cells are prone to dysfunction induced by multiple pathological factors, which is manifested by an impaired vasomotor function, thrombosis, and arterial wall proliferation. Studies have shown that vascular endothelial dysfunction is closely related to the occurrence and development of cardiovascular diseases such as atherosclerosis and heart failure. Therefore, effectively evaluating endothelial functions is essential to prevent and treat cardiovascular diseases. In this review, we discuss the functions and regulatory principles of the vascular endothelium and its relationship with cardiovascular diseases and summarize the basic principles and advantages and disadvantages of existing endothelial assessment techniques to assist in the diagnosis and treatment of cardiovascular diseases.