Objective：To investigate the protective effects of rapamycin on cerebral ischemia-reperfusion injury in rats，with the model of global cerebral ischemia-reperfusion established by means of ligating bilateral carotid arteries. Methods：Cerebral ischemia was produced by transient occlusion of bilateral carotid arteries for 20 minutes. The rapamycin treated group received an intracerebroven－tricular injection of rapamycin（10 mmol/L） 30 minutes and 12 hours before cerebral ischemia.Serial coronal sections of the brains were collected every 250 ?滋m 24 hours after ischemia-reperfusion，then each frozen brain slice was selected to stain using cresyl violet and observed under light microscope unbiased counting method was used to calculate the cell density of the sham-operation （SO） group，treatment control （TC） group and rapamycin injection （RI） group. Results：①The cells of prefrontal cortex and temporal lobe in the molecular layer in TC group reduced obviously compared with SO group（P<0.05）.②The cell density of the temporal lobe molecular layer in RI group 12 hours before ischemia increased significantly compared with TC group（P<0.05）.③The cell density of the pre－frontal cortex in RI group both 30 minutes and 12 hours before cerebral ischemia was higher than that in TC group and the increase in RI group 12 hours before cerebral ischemia was much more significant（P<0.05）. Conclusion：Rapamycin has protective effects a－gainst cerebral ischemia-reperfusion injury in rats，and the protective effects are closely related to the administration time.