In-stent restenosis (ISR) is a common clinical complication after carotid artery stenting (CAS) and a major risk for a stents fatigue life. Duplex ultrasound (DUS) is widely used for the preliminary evaluation and follow-up of extracranial carotid artery disease, but DUS stenosis grading is mainly based on the original or nonsurgical carotid artery. That grading may not be applicable to carotid artery stenosis after CAS. The study intended to investigate the predictive value of quantitative analysis of results from the DUS examination in the evaluation of ISR following CAS. The research team designed a control analysis of result samples. The study took place in the Ultrasound Department at the Affiliated Yantai Yuhuangding Hospital of Qingdao University in Yantai, Shandong, China. Participants were 103 patients who underwent carotid artery stenting (CAS) between March 2017 and April 2018 at the hospital. The study used Doppler DUS and digital subtraction angiography (DSA) of the carotid artery at 12 months postoperatively to analyze the consistency of DUS and DSA in the evaluation of ISR. Taking the results of the DSA examination as the standard, the research team analyzed the differences between those results and the indicators from the DUS examination for participants with different severities of stenosis. The research team plotted the receiver operating characteristic curve (ROC) and evaluated the diagnostic efficiency of DUS indicators in the determination of restenosis, including diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value. The DSA examination showed that stenosis severity was 0%-30% for 51 participants, 31%-50% for 27 participants, 51%-80% for 16 participants, and≥ 80% for 9 participants. The DUS showed that stenosis severity was 0%-30% for 35 participants, 31%-50% for 38 participants, 51%-80% for 22 participants, and≥ 80% for 8 participants. The consistency was found to be Kappa (к)= 0.74. Taking the DSA as the standard, the peak systolic velocity (PSV), end diastolic velocity (EDV), peak systolic velocity of the internal carotid artery/peak systolic velocity of the common carotid artery PSVICA/PSVCCA) significantly increased in participants with a stenosis severity of 51-80% and> 80%, compared with those with a stenosis severity of< 50%, and the difference was statistically significant (P<. 05). The ROC curve showed that the area under curve (AUC) of the PSV predicting restenosis at a≥ 50% severity was significantly higher than those of the EDV and PSVICA/PSVCCA (P<. 05). Where the optimal cut-off-off point for the PSV was 195 cm/s, the ROC curve showed that the AUC of the PSV predicting restenosis at an≥ 80% severity was significantly higher than that of the EDV and PSVICA/PSVCCA (P<. 05). Where the optimal cut-off point for the PSV was 280 cm/s, the PSV had significantlyhigher diagnostic accuracy, sensitivity, and positive predictive value than the EDV and PSVICA/PSVCCA in evaluating the restenosis at a severity of≥ 50% and≥ 80%. Doppler DUS can effectively evaluate restenosis after carotid artery stenting (CAS), where a PSV≥ 195 cm/s and 280 cm/s can be used as the reference indicators for≥ 50% and≥ 80% restenosis.(Altern Ther Health Med. 2023; 29 (1): 52-57).