The purpose of the present study is to measure the effect of Tuber Pinelliae on EP(epinephrine) induced contraction of isolated rat thoracic aorta. Contractile force was measured with force displacement transducer under 1.5g loading tension. The mean percent increasing of rCBF was 11.4% (p<0.05) after 10㎎/㎏ Tuber Pinelliae. Contractions evoked by EP (ED50) and KCI 65.4mM were decreased significantly by Tuber Pinelliae. L-NNA, ODQ and atropine significantly altered the effect of Tuber Pinelliae, but propranolol and indomethacin did not change the relaxation of Tuber Pinelliae. These results indicate that Tuber Pinelliae can relax EP and KCI induced contraction of isolated rat thoracic aorta and that this decreasing contraction related to epithelium, nitric oxide, and parasympathetics.