Abstract： Objective To explore the cerebral vasoreactivity (CVR) changes before and after middle cerebral artery stenting (MCAS) and the relationship between thrombolysis in yocardial infarction(TIMI)flow grade and CVR. Methods Thirty-nine patients with middle artery stenosis received MCAS treatment were selected as operated group and 48 non-stroke hospitalized patients at the same period as control group. Transcranial Doppler (TCD) combined with CO2 inhalation test was performed to assess the changes of CVR before and after MCAS. Digital subtraction angiography (DSA) was employed to assess the TIMI flow grade. These data were statistically analyzed. Results As compared with that of the control group, preoperative CVR of the operated group was significantly reduced (P<0.05); the postoperative CVR significantly increased as compared with the preoperative one in the operated group (P<0.05); preoperative CVR was positively correlated with the TIMI grade (R=0.594, P<0.05). Preoperative CVR had a significant difference between TIMI grade 1 and TIMI grade 2 (P<0.05), but not between TIMI grade 2 and TIMI grade 3 (P>0.05). The degree of CVR improvement was negatively correlated with the TIMI grade (R=-0.620, P<0.05) and preoperative CVR (R=-0.760,P<0.05). Conclusion MCAS can effectively improve the CVR.