Abstract: Objective To observe the expression of complement regulatory protein CD59 in mice with cerebral ischemia-reperfusion(I/R) injury and its significance. Methods A mouse middle cerebral artery occlusion (MACO) model was established with filament method. One hour after ischemia, the mice were subjected to reperfusion. Their cranial neurological deficit and brain tissue pathological lesion were recorded. Expression of complement regulatory protein CD59 was detected by immunohistochemistry and RT-PCR, respectively. Results The neurological deficit score was 2.166 7±0.408 3, 0.833 3±0.408 3 and 0, respectively, at 24, 72 and 96 h after reperfusion. The brain tissue pathological lesion was the severest at 24 h after reperfusion. The expression level of complement regulatory protein CD59 was the lowest at 24 h and almost retuned to normal at 96 h after reperfusion. The expression level of complement regulatory protein CD59 was negatively related with brain pathological injury and neurological deficit score. Conclusion The expression level of complement regulatory protein CD59 changes significantly after cerebral I/R, indicating that CD59 may be involved in cerebral I/R injury.