Abstract: OBJECTIVE Study effect of tetra-acetylated puerarin on isolated rats thoracic aortic rings and it's mechanisms. METHODS The thoracic aortic rings of Sprague-Dawley rats were mounted on a perfusion system, and isometric tensions of the aorta rings precontracted with noradrenaline bitartrate (NA) and potassium chloride (KCl) respectively were recorded in vitro. RESULTS Compared with the controls, tetra-acetylated puerarin showed significantly different vasodilation effects on NA-precontracted aortic ring (P<0.01) in normal rats; it showed significantly different vasodilation effects on KCl-precontracted aortic ring (P<0.01), and show significantly different vasodilation effects on aortic ring with or without endothelium (P<0.01) in the same molar concentration; it showed no significantly different vasodilation effects on vascular muscle induced calcium-free solution and normal calcium solution (P>0.05). CONCLUSION Tetra-acetylated puerarin can inhibit the receptor-operated calcium channel and voltage-dependent calcium channel, and it's vasodilator may be related to blood vessel endothelium.