Objective To observe the effects of amyloid-β (Aβ) receptor PirB on mouse astrocyte proliferation and reactive astrogliosis in vitro. Methods Mouse primary astrocytes were cultured, and divided into control group, Aβ group, Aβ+0.2 μmol/L PEP group, Aβ+0.4 μmol/L PEP group, Aβ+Fluspirilene group, Aβ+GFP-LV group, and Aβ+mPirB-LV group. The mouse astrocytes were treated with soluble PirB extracellular peptide PEP or PirB inhibitor Fluspirilene, respectively, to inhibit endogenous PirB receptor, or overexpressed PirB gene via lentivirus transfection and then treated with Aβ_1-42 oligomers. The proliferation of astrocytes was observed by RTCA and EdU methods, and the mRNA expression levels of S-100 calcium-binding protein B (S-100β), Vimentin, Nestin and amyloid precursor protein (APP) associated with reactive astrogliosis of astrocytes were observed by real-time PCR, and the expression level of glial fibrillary acid protein (GFAP) was detected by Western-blotting. Results The results of RTCA monitoring showed that normalized cell index (NCI) values of each group decreased sharply after treatment, and then increased gradually and tended to be stable. The results of EdU staining showed that the proliferative activity of astrocytes was significantly enhanced in the Aβ group (P<0.05) compared with control group; Compared with Aβ group, cell proliferation activity in Aβ+0.2 μmol/L PEP group, Aβ+0.4 μmol/L PEP group and Aβ+Fluspirilene group were significantly decreased (P<0.01 or P<0.001). The results of real-time PCR showed that compared with control group, mRNA expressions of GFAP, S-100β, Vimentin, Nestin, APP and PirB in Aβ group were significantly increased (P<0.05); Compared with Aβ group, mRNA expressions of GFAP, S-100β, Vimentin, Nestin, APP and PirB in Aβ+0.4 μmol/L PEP group were significantly decreased (P<0.01); Compared with Aβ+GFP-LV group, mRNA expressions of GFAP, S-100β, Vimentin, Nestin, APP and PirB in Aβ+mPirB-LV group were significantly increased(P<0.05). The results of Western blotting showed that compared with control group, the expression of GFAP in Aβ group was significantly increased (P<0.05); Compared with Aβ group, the expression of GFAP in Aβ+0.4 μmol/L PEP group was significantly decreased (P<0.05). Conclusions PirB is an upstream molecule which could regulate astrocyte proliferation and reactive astrogliosis, and inhibiting PirB receptor in astrocytes may be a potential treatment for Alzheimer's disease.