Ｏｂｊｅｃｔｉｖｅ　To evaluate cerebral perfusion with the bilateral cerebral oxygen saturation(rSO2) monitoring in patients with acute ischemic stroke (AIS) after endovascular thrombectomy (EVT).　Methods　Patients with AIS who received EVT, aging over 18 with American Society of Anesthesiologists(ASA) grade Ⅰ-Ⅳ were selected for this study. There were total 24 patients enrolled in this observational study. They were divided in two groups according to extent of thrombolysis in cerebral infarction（TICI）. Patients with TICI≥2b (17 cases) were divided into good recanalization group whereas patients with TICI≤2a（7 cases）were divided into poor recanalization group. Conscious sedation or general anesthesia was performed according to individual situation. We monitored bilateral regional rSO2 and calculated the values of difference: ΔrSO2 is rSO2 of healthy side minus rSO2 of suffering side. The percentage of difference of bilateral rSO2 (%rSO2) is %rSO2=ΔrSO2/health lateral rSO2. Both ΔrSO2 and percentage of rSO2 were monitored and recorded at different time points: before thrombectomy (T1), 5 min (T2), 15 min(T3) and 30 min (T4) after thrombectomy. Meanwhile, TICI would be evaluated via digital subtraction angiography with intervention by physician. The correlation between ΔrSO2 and TICI was calculated using pearson′s correlation analysis and receiver operating characteristic curve (ROC). The correlation between %rSO2 and TICI was calculated with same method.　Results　Twenty four patients was enrolled in this study, 17 patients obtained good cerebral blood flow reperfusion with TICI≥2b (good recanalization group) while 7 patients with poor recanalization (TICI≤2a, poor recanalization group). ΔrSO2 and %rSO2 of patients in good recanalization group were decreased significantly after thrombectomy (T2, T3, T4) compared with the values of T1 (P＜0.05). There were no significant changes in poor recanalization group (P＞0.05) at the same time points (T2, T3, T4). Compared with the values of good recanalization group, ΔrSO2 and %rSO2 were significantly higher at T2, T3, T4 time points than T1 time point (P＜0.05). The correlation between ΔrSO2 and TICI was also negative correlation, r=－0.78(P=0.00). Similarly, the correlation between %rSO2 and TICI was also negative correlation, r=－0.79(P=0.00). The area under the receiver operating characteristic curve (AUC) of ΔrSO2 and %rSO2 were 0.987 (95%CI 0.973－1.000) and 0.988 (95%CI 0.976－1.000) respectively. The cut off values were 7% and 10% respectively. The values of sensitivity and specificity of ΔrSO2 were 0.933 and 0.988 respectively. The sensitivity and specificity of %rSO2 were 0.933 and 0.996 respectively.　Conclusions　The changes of ΔrSO2 and %rSO2 reflect cerebral perfusion and have potential clinical values in assessing cerebral perfusion variation in patients with AIS after EVT.