Objective:To investigate the dynamic changes of vascular adventitia and smooth muscle cell(SMC) proliferation and collagen distribution in the vein graft restenosis model. To evaluate the effects of adventitia,cell proliferation and collagen distribution on vascular remodeling. Methods:The pig autogenous vein grafts restenosis model was constructed. Specimens were harvested at three time points that was 7th,30th and 45th days. According to the Masson staining slices,the vascular remodeling,proliferation index of adventitia cell and SMC,and collagen distribution were investigated by histomorphometrical and immunohistochemical approach. Results:①At 7thd after operation,the neointima formed and continuously thickened,whose thickness reached maximal at 45thd after operation. The thickness and cell density of adventitia increased gradually at 7thd,which reached peak at 30thd after operation. But in the 45thd group,they were smaller than those in the 30thd group. According to PCNA stain,the proliferation index of adventitia cell and SMC increased significantly at 7 d after operation,which reached peak at 30thd,whereas the expression of PCNA reverted toward the baseline at 45thd after operation. ②At 7thd after operation,the collagen of adventitia and neointima gradually increased,which of neointima at the 30th and 45thd group increased more significantly than the control and 7thd group(P < 0.05). The collagen of adventitia reached maximal at 30thd,but at 45thd,they were smaller than those at 30thd after operation(P < 0.05). ③ The luminal area and internal elastic lamina gradually decreased after operation,which in the 30thd and 45thd group reduced significantly compared with the control group and 7thd group(P < 0.05). But the residual restenosis rate changed inversely compared with the luminal area. Remodeling index and external elastic lamina slightly increased at the 7thd group,but reduced gradually after that,which in the 30thd and 45thd group decreased significantly(P < 0.05). Conclusion:The changes of vascular adventitia and smooth muscle cell proliferation,the thickness and fibration of adventitia and rearrangement of collagen are the important factors on intimal hyperplasia and vascular remodeling,which takes part in and accelerate the course of vein restenosis.