Abstract: Neuroinflammation mediated by microglia is essential for the occurrence and development of Alzheimer’s disease (AD). Through the analysis of the GEO database, it was found that IL-27 expression decreased in both the cerebral cortex and hippocampus of AD patients. In this study, the AD cell model of BV-2 cells injured by Aβ_1-42, the inflammatory cell model of BV-2 cells damaged by LPS, and the inflammatory animal model were established and the effects of IL-27 after its administration in the above models in regulating microglial phenotype and neuroinflammation were evaluated. In the animal models, the number of Iba1+ microglia in the hippocampus was detected by immunohistochemistry, the expression of pro-inflammatory factors such as TNF-α, IL-1β and IL-6 was detected by qPCR, ELISA and Western blot, and the expression of M1/M2 phenotypic markers in microglia was detected by qPCR. To further explore the action mechanism of IL-27, Western blot was used to detect the expression levels of NF-κB, p-NF-κB, IκBα and p-IκBα in microglia after administration of IL-27 and Aβ_1-42. The results showed that IL-27 alleviated the abnormal activation of microglia induced by lipopolysaccharide (LPS), decreased the expression of pro-inflammatory factors such as TNF- α, IL-1β and IL-6, transformed microglia induced by LPS or Aβ_1-42 from neurotoxic M1 to neuroprotective M2, and improved the abnormal phosphorylation of NF-κB and IκBα induced by Aβ_1-42. The research suggested that IL-27 can regulate the M1/M2 polarization of microglia induced by Aβ_1-42 or LPS, and alleviate neuroinflammation.