Objective To reveal the morphological changes, zero-stress state, apoptosis and dedifferentiation of vascular smooth muscle cell(VSMC)of the arterial wall during vascular remodeling induced by alterations of flow shear stress. Methods The ligation on some distal branches of left carotid was clone in the one and same rat to induce low shear stress state in the left common carotid artery(LCA)and high shear stress state in the right common carotid artery (RCA), while the rats with sham-operation without ligation were used as the normal control. The arterial morphology was examined by light microscopy and Transmission Electronic Microscope (TEM). Open angle was measured under the zero stress state. The apoptotic cells were detected by TdT-mediated dUTP-biotin nick end labeling (TUNNEL) staining. The expression of h1-calponin, which is a marker for the differentiated state of VSMC, was inspected with Western blotting. Results At 7(superscript th) day after operation of the LCA, the inner diameter was decreased about 13%, the ratio of wall thickness to inner diameter was increased significantly and the open angle was reduced. Otherwise, the thickness of sub-endothelial and VSMC apoptotic were significantly increased while the h1-calponin decreased significantly. Conclusion The significantly decreased shear stress could induce the vascular remodeling in a short time. The apoptosis and dedifferentiation of VSMC might be one of early events during the vascular remodeling induced by low flow or low shear stress.