Nitroglycerin is a nitrate class of Western medicine, can directly relax the vascular smooth muscle, especially small blood vessel smooth muscle, can dilate peripheral blood vessels, so that peripheral resistance is reduced, the amount of return blood decreased, cardiac output is reduced, the heart load is reduced, so that the myocardial oxygen consumption is reduced, and then get the relief of angina pectoris. In addition, nitroglycerin can also promote the formation of collateral circulation, sublingual administration of rapid onset of action, can be maintained for 30 minutes, other smooth muscle also has a relaxing effect, can be appropriate to lift the biliary colic, pyloric spasm, renal colic and so on, but the effect of time is relatively short.