Objective To evaluate the effect of 3D pCASL on hemodynamics in patents with moyamoya disease before and after STA-MCA revascularization. Methods 44 patients with moyamoya disease treated by STA-MCA revascularization in our hospital were selected as the subjects and the brain perfusion imaging was performed by MRI 3D pCASL perfusion with PLD of 1.5s and 2.5s. The ASL perfusion images of the patients were observed before and after operation, and the cerebral blood flow (CBF) and relative cerebral blood volume(rCBF) were analyzed between pre-operative and postoperative, and between operative side and non-operative side in the cerebral ischemia area. Results Of the 44 patients, 24 underwent left bypass, 20 right bypass, 30 first bypass and 14 second bypass. The dynamic changes of cerebral blood flow perfusion before and after operation were observed by ASL perfusion images . In different PLD time, the CBF value of the operative side and the non-operative side increased significantly on postoperative, and the difference between the pre-operative and post-operative had significant statistical significance (P<0.05). There was no significant difference in operative side and non-operative side on pre-operative(P>0.05). The CBF value of operative side was significantly higher than that of non-operative side on post-operative(P<0.05). The ratio of the operative side to the non-operative side was relative cerebral blood flow (rCBF). In different PLD time, the rCBF value increased significantly after operative. The difference between the pre-operative and post-operative was statistically significant (P<0.05). Before and after operation, there was no significant difference in rCBF values between PLD=1.5s and PLD=2.5s (P>0.05). Conclusion Dual-delay MRI 3D pCASL can dynamically display the hemodynamic changes in patients with moyamoya disease, and can effectively evaluate the improvement of cerebral blood flow in patients with moyamoya disease after STAMCA. It is of great significance to evaluate the hemodynamic changes in patients with moyamoya disease after vascular reconstruction.