To observe regulatory effects of Astragalus Polysaccharide(APS）on directional differentiation of C17.2 neural stem cells in vitro.Methods:Cultivation system and differentiation model of C17.2 neural stem cells were established in vitro.APS intervention group and PBS control group were set up.Immunofluorescence staining was used to detect expression levels of Nestin，GFAP，MBP and NeuN，the simbolic marker proteins of neural stem cells，astrocytes，oligodendrocytes and neurons，so as to explore the regulatory effects of APS on directional differentiation of C17.2 neural stem cells.Results:Compared with the PBS control group，the expression levels of Nestin and GFAP proteins in the APS intervention group were down-regulated while the expression levels of MBP and NeuN proteins were up-regulated.The differences were statistically significant(P<0.05).APS down-regulated the expression level of Nestin protein in the differentiation model，which meant it could inhibit the stemness maintenance of C17.2 neural stem cells and lead them to enter the differentiation state.APS down-regulated the expression level of GFAP protein，and up-regulated the expression levels of MBP and NeuN proteins，which meant it could promote C17.2 neural stem cells to differentiate into oligodendrocytes and neurons directionally，and inhibit them to differentiate into astrocytes.Conclusion:APS can effectively regulate the directional differentiation of C17.2 neural stem cells in vitro，which suggests that it might be a potential drug for the treatment of neurodegenerative diseases.