Abstract: AIMTo study the protective effect and mechanism of osthol on learning and memory impairment of mice with acute senile model induced by AlCl₃. METHODSAfter sc AlCl₃ 60 mg·kg^-1 for 7 d and ip osthol 15 and 7.5 mg·kg^-1 for 12 d, using step-through test and step-down test, the effect of osthol on learning and memory was observed and the glutathione peroxidase (GSH-PX) activities in blood and superoxide dismutase (SOD) activities in plasma and cerebrum were measured. RESULTSOsthol 15 and 7.5 mg·kg^-1 significantly improved the capability of memory and enhanced the activities of GSH-PX and SOD in AlCl₃ treated mice. CONCLUSIONOsthol shows protective effect on brain memory impairment of mice in acute senile model induced by AlCl₃. Perhaps the mechanism is involved in enhancing the activities of GSH-PX and SOD, clearing away the free radical, protecting the brain neuron from the harm of lipoperoxide.