Abstract: OBJECTIVE To observed effects of water extract from Portulacu oleracea L. of learning behavior and SOD, Acetyl cholinesterase(AchE) activities, MDA content in brain tissue of Alzheimer’s disease(AD) mice are caused by AlCl₃. METHODS The mice 6 of groups of 2 batches: control group, model group, piracetam(3.0 g·kg^-1) group and 3 groups of water extract from Portulacu oleracea L. (2.6, 1.3, 0.65 g·kg^-1). Normal control group PO saline. Copied AD mice models by PO AlCl₃ 200 mg·kg^-1 for 40 d. Observed the learning memory improvement of passive avoidance with darkness avoidance test and water maze test, and determined contents of MDA, activities of SOD and AchE in brain tissues of mice. RESULTS The different concentration water extract from Portulacu oleracea L. could significantly prolong latency and reduce for error frequency of mice, it could obviously short times of arriving water maze and reduce for error frequency of mice than model group. It could substantially improve SOD activity, reduce AchE contents and activity MDA in brain tissues of mice. CONCLUSION The water extracts from Portulacu oleracea L. have obvious improvement effects of learning memory in AD model mice, its mechanism may be related to improves SOD activity, to reduce MDA content and AchE activity.