Aim to investigate the changes of cerebral microcirculation after subarachnoid hemorrhage (SAH) and its association with cerebral vasospasm (CVS) after SAH. CTP was performed in 85 patients with SAH and 35 controls. Cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) were recorded for final analysis. CTP parameters were compared between (1) SAH group and control group, (2) CVS group and non-CVS group (nCVS), (3) symptomatic CVS (sCVS) group and asymptomatic CVS (asCVS) group. Compared to control group, there were significant differences in CBF and MTT of SAH patients (P < 0.05). Among SAH patients, the CBF and MTT (a decreased CBF and a prolonged MTT) of CVS patients were significantly different from those of non-CVS patients (P < 0.05). In 46 CVS patients, sCVS group presented significantly lower CBF and more prolonged MTT than asCVS patients (P < 0.05). Seven cases with MTT between 6.31 and 12.72 s showed delayed ischemic neurological deficit (DIND), two of whom had hemiplegia, and one died. Our findings suggest that CTP examination contributes to uncover the changes of cerebral microcirculation after SAH, and the changes of cerebral microcirculation are associated with CVS post SAH.