Previous study showed that D-galactose (D-gal) increased production of Reactive Oxygen Species and resulted in impairment of memory and cholinergic system. Piliostigma reticulatum has been reported to have many benefits and medicinal properties. In this study, we evaluated the protective effect the aqueous extract of Piliostigma reticulatum against Dgalactose-induced memory loss, impairment of cholinergic system and oxidative damage. Our results displayed that Piliostigma reticulatum administration significantly improved behavioral performance of D-gal-treated mice in morris water maze task and open field test. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione content (GSH) in D-galactose-treated mice were enhanced, while the content of the lipid peroxidation product malondialdehyde (MDA) was decreased by the plant administration. Furthermore, our results also showed that Piliostigma reticulatum significantly inhibited cholinesterase (AchE) activity, increased the level of acetylcholine in the brain of D-gal-treated mice, which could help restore impairment of brain function.