Alzheimer's disease (AD) is a great threat for the health and life of elderly people. MicroRNA-128 (miR-128) has been reported to be abnormally expressed in the brain of AD patients and associated with the pathogenesis of AD. Our study aimed to have a deep insight into the roles and molecular basis of miR-128 in the development and progression of AD. The cognitive ability and exploratory behaviors were assessed by morris water maze and open-field tests, respectively. The concentrations of amyloid-β (Aβ) 40, Aβ 42, tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-10 and activity of β-secretase and α-secretase were determined by corresponding ELISA commercial kits. RT-qPCR assay was performed to detect miR-128 level and the mRNA expression of peroxisome proliferator-activated receptor gamma (PPARγ), ionized calcium-binding adaptor molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP). Western blot assay was conducted to determine protein expression of PPARγ, amyloid precursor protein (APP), β-APP cleaving enzyme (BACE1), sAPPα and sAPPβ. The effect of miR-128 and PPARγ on amyloid plaque formation was assessed by immunohistochemistry assay. PPARγ mean optical density was determined by immunofluorescence assay. The interaction between miR-128 and PPARγ were validated by bioinformatics analysis and luciferase reporter assay. We found AD mice showed AD-like performance and an increased cerebral cortex Aβ production. MiR-128 expression was upregulated and PPARγ expression was downregulated in cerebral cortex of AD mice. Moreover, PPARγ was a target of miR-128. Additionally, miR-128 knockout or PPARγ upregulation inhibited AD-like performances, amyloid plaque formation, Aβ generation, APP amyloidogenic processing and inflammatory responses in AD mice, while these effects of miR-128 knockout were abrogated by PPARγ inhibitor. The results indicated MiR-128 knockout weakened AD-like performances, and reduced Aβ production and inflammatory responses by targeting PPARγ in AD mice.