Objective To study multi-slice spiral CT imaging diagnosis of moyamoya disease and the changes of cerebral blood flow before and after conservative intervention. Methods 32 patients with moyamoya disease treated in our hospital from January 2011 to May 2015 were studied. All of them underwent CT examination before and after conservative intervention. CT imaging features were observed, including volume rendering (VR), maximum intensity projection (MIP), curve planar reformation (CPR) and multi planar reconstruction (MPR). The changes of cerebral blood flow before and after the conservative intervention were compared, including cerebral blood flow (CBF), regional cerebral blood flow (rCBF), cerebral blood volume (CBV), contralateral cerebral blood volume (rCBV), time to peak (TTP) and contralateral time to peak (rTTP). Results There were no statistically significant differences in rCBF, CBV, rCBV and rTTP before and after the treatment (P>0.05). CBF after the treatment was higher than that before the treatment while TTP was lower than that before the treatment (P<0.05). Conclusion The application of multi-slice spiral CT perfusion imaging in moyamoya disease is beneficial to clearly show the imaging features and make a definite diagnosis. It is a non-invasive and efficient examination way. Through observing the changes of cerebral blood flow in patients, the curative effect can be determined and the prognosis can be judged. It is affordable and worthy of application.