Objective: To investigate the value of color Doppler ultrasound in evaluating the efficacy of carotid artery stenting (CAS) and residual stenosis after operation. Methods: A total of 110 CAS patients treated in the neurosurgery department of Chizhou People’s Hospital from January 2018 to September 2020 were prospectively selected, and the relevant measurement indexes of ultrasound before and after operation were compared. According to digital subtraction angiography (DSA), the incidence of postoperative residual stenosis was analyzed and divided into residual stenosis group and normal group (no residual stenosis). The clinical data and ultrasound related indexes were compared between the two groups, and the influencing factors of residual stenosis after CAS were analyzed. Results: The stenosis degree of stenosis site after CAS was (26.51±5.78)%, which was lower than that before [(83.57±10.20)%]. The peak systolic velocity (PSV) and end diastolic velocity (EDV) of proximal and distal carotid artery after CAS were significantly lower than those before CAS (P<0.05). DSA confirmed that the incidence of residual stenosis was 22.73%. PSV [(131.48±11.92) cm/s] and EDV [(47.20±5.24) cm/s] in the residual stenosis group were significantly higher than those in the normal group [(98.86±10.26) cm/s and (38.14±5.06) cm/s]. The plaque morphology was irregular (76.00%) and plaque calcification (72.00%) in the residual stenosis group were significantly higher than those in the normal group (38.82% and 61.18%) (P<0.05). Multivariate logistic regression analysis showed that irregular plaque shape (OR=1.572, 95%CI: 1.021–2.256) and plaque calcification (OR=2.380, 95%CI: 1.364–3.527) were independent risk factors for postoperative residual stenosis in patients with CAS (P<0.05). Conclusion: Color Doppler ultrasound can effectively evaluate the effects of CAS recanalization and observe whether there is residual stenosis. Irregular plaque shape and plaque calcification are the risk factors of residual stenosis after CAS.