Objective To explore the effect of Rab27b on the secretion of brain-derived neurotrophic factor （BDNF） in mouse astrocytes. Methods Quantitative PCR and immunofluorescence staining were used to detect the mRNA expression and distribution of Rab27a and Rab27b， two subtypes of Rab27 molecules， in the cerebral cortex and hippocampus of wild-type mice. Immunofluorescence staining was used to detect the expression of Rab27b in astrocytes in the hippocampus of wild-type mice. Western blot method was used to detect the expression of BDNF in astrocytes and PSD95 and Synapsin1， synaptic plasticity markers in the hippocampus of Rab27b gene knockout mice. Enzyme-linked immunosorbent assay （ELISA） method was used to detect the secretion of BDNF in astrocytes of Rab27b gene knockout mice， and to clarify the effect of Rab27b gene knockout on BDNF secretion levels in astrocytes. Results The results of quantitative PCR and immunofluorescence staining showed that the mRNA levels and fluorescence intensity of Rab27b in the cerebral cortex and hippocampus of wild-type mice were higher than those of Rab27a， and the differences were statistically significant （P＜ 0.01）. The immunofluorescence results showed that Rab27b was co expressed with the astrocyte marker GFAP. Western blot results showed that there was no statistically significant difference in the total amount of BDNF in astrocytes of Rab27b gene knockout mice compared to wild-type mice （P＞ 0.05）. The ELISA results showed that the secretion level of BDNF in astrocytes of Rab27b gene knockout mice was lower than that of wild-type mice， and the difference was statistically significant （P ＜ 0.05）. Western blot results showed that the expression levels of PSD95 and Synapsin1 in the hippocampus of Rab27b gene knockout mice were lower than those of wild-type mice， and the differences were statistically significant （P ＜ 0.01）. Conclusions Rab27b regulates the secretion of BDNF from mouse astrocytes and improves synaptic plasticity.