Abstract: The operation of ring constraining, which produce a symmetricalstenosis to artery, was a usually used method to establish an animal modelor in vitro arterial atherosclerosis model because the straitness degree canbe controlled easily and quantitatively. However, it is unknown howthe flow field will be changed, and whether the flow field is similar tothat under physiological stenosis when a ring constraining employed tobifurcation or bended artery. To understand the flow in bifurcation arteryunder a ring constraining, carotid bifurcation with a symmetrical stenosisto the carotid sinus was instanced. The velocity profile, the secondary flowand the distribution of wall shear stress in the stenosed carotidbifurcation were numerically studied. The results were compared withthose inthe healthy carotid bifurcation. It was shown that the flow field in thecarotid sinus, especially, the distribution of wall shear stress, waschanged. Low wall shear stress was axis-symmetrically distributed on thewall of the backward site of stenosis. Based on the influence of low wallshear stress on atherosis, it was prompted that atherosis might take placeaxis-symmetrically in the backward site of stenosis. It is obviouslydifferent to the physiological process of atherosis. Therefore, it isindicated that the symmetrical stenosis is not suitable for simulating thecarotid sinus stenosis. To simulate the physiological stenosis in thecarotid sinus, an asymmetrical stenosis should be employed.