Abstract: The protective effect of hyperin (Hyp) against cerebral ischemia-reperfusion injury was studied. On the cerebral ischemia-reperfusion model in mice, Hyp(50, 100 mg·kg^-1, ip) was shown to markedly and dose-dependently inhibit the decrease of lactate dehydrogenase (LDH) in cerebrum and improve the learning and memory impairment on the step down test. On the fourvessel occlusion model in rats, Hyp(50 and 100 mg·kg^-1, ip) significantly reduced the decreases of glutathione peroxidase(GSH-Px), superoxide dismutase(SOD) and LDH activities in the cerebrum.Hyp was also shown to inhibit the increase of nitric oxide (NO) and malondialdehyde (MDA) contents in the cerebrum and promote the recovery of EEG activities. These results suggest that Hyp has protective effect against cerebral ischemia-reperfusion injury via attenuating free radical and NO.