Objective Carotid artery stenosis is one of the major causes of stroke, and the mainstream solutions include endarterectomy and carotid stenting, but both of them have certain shortcomings. In this case, transcarotid ?a?rtery ?revascularization (TCAR) with reverse flow protection has been proposed clinically to treat carotid artery stenosis while theoretically circumventing the drawbacks of the original method. One of the difficulties of TCAR is the resistance valve, where too large a value of resistance can lead to insufficient reverse flow of blood, and too small a value of resistance can lead to cerebral ischemia. Methods In this study, based on the computational fluid dynamics method, we performed TCAR surgical simulation on a vascular model of a patient with posterior circulation loss, adjusted the inner diameter of the resistance column in the catheter, and quantitatively analyzed the effect of the inner diameter of the resistance column on the major arteries as well as the blood flow in the catheter. Results Blood flow on the unstented side was not sensitive to changes in resistance column ID, internal carotid artery flow on the stented side decreased monotonically with increasing resistance column ID, external carotid artery flow on the stented side increased monotonically with increasing resistance column ID, catheter flow decreased substantially with increasing resistance column ID, and the closer the stenosis occurred, the more sensitive blood flow was to changes in resistance column ID. Conclusions In this paper, a patient-specific numerical simulation model of TCAR was established based on clinical data, which can assess the intraoperative effects of TCAR to some extent and has potential clinical applications.