Abstract: Objective: To explore the protective effect and mechanism of magnesium sulfate on global cerebral ischemia/reperfusion injury on mice.Methods: One hundred KM mice were randomly divided into sham operation group,ischemia/reperfusion group and magnesium sulfate groups (low dosage group,medium dosage group and high dosage group).Global cerebral ischemia was made by blocking bilateral common carotid artery and pressing soft tissues in carotid for 30 min.After one-hour reperfusion,the mice were killed.The content of nitric oxide (NO),activities of nitric oxide synthase (NOS),Ca²⁺-Mg²⁺-ATPase and Na⁺-K⁺-ATPase were measured and the pathologic changes of the brain tissues were observed.Results: Compared to ischemia/reperfusion group,NO content and NOS activity of brain tissue decreased the different dosages of magnesium sulfate,and enhance the activities of Ca²⁺-Mg²⁺-ATPase and Na⁺-K⁺-ATPase (P<0.05-P<0.01).Conclusions: The pretreatment of magnesium sulfate could obviously relieve cerebral ischemia/reperfusion injury by decreasing the content of NO and activity of NOS and increasing the activities of Ca²⁺-Mg²⁺-ATPase and Na⁺-K⁺-ATPase.