Objective To observe the effects of the chronic adventitia injury on the vasoconstriction of the rat carotid artery. Methods A non-occlusive silicone collar was positioned around the right carotid artery of rats. Blood flow and vascular reactivity to 5-HT were examined, and both carotids were harvested for morphometry at day 3,7 and 14 after operation. Results In the early stage of advenfitia injury induced by positioning a silicone collar around file rat carotid artery, there appeared the characteristic histological changes of chronic vasospasm in collared artery, such as the reduction of the luminal area for （12.15±2.29）% at day 3 after operation （P =0.003 ） and （45.17±3.84）% at day 7 （P 〈 0.001 ）] ,corrugation of the internal elastic lamina,medial thickening up to [ （23.04±5.96）% at day 3 （P =0.009）, （61.65±10.32）% for day 7 （P 〈 0.001 ）] ,the reduction of the blood flow and the increase of vascular reactivity to 5-HT when compared to con- tralateral arteries. Two weeks after collar placement, the vascular wall remodeling was observed in injured artery, such as the medial thickening for [（31.52±4.56） %,P =0.012] and a diffuse intimal hyperplasia,the reduction of the lunfinal area [（37.17±4.57）% （P 〈 0.001）] and the carotid artery blood flow. The average neointima area was （0.19±0.05） rom2 in collared arteries. The vascular reactivity to 5-HT came back to the normal level. Conclusions Collar-induced advenfitia injury caused the enhancement of vascular contractility and the neointima formation. The change of vascular contractility appeared before the formation of neointima.