AT-II is medically referred to as angiotensin II, a peptide vasoactive substance in the body that is a component of the renin-angiotensin-aldosterone system. Angiotensinogen can be converted to the less active angiotensin I by the action of renin, and angiotensin I can be converted to angiotensin II by the action of angiotensin converting enzyme. Angiotensin II is one of the most important vasoconstrictor substances, and its binding to angiotensin receptors can cause vasoconstriction, increase resistance and raise blood pressure. In addition, angiotensin II can also stimulate the synthesis and secretion of aldosterone in the adrenal cortex, which acts on the distal convoluted tubules and collecting ducts to promote the reabsorption of sodium and water and the excretion of potassium ions, i.e., the role of sodium and potassium conservation, and has an important role in maintaining the body’s water and salt balance.