Objective: To observe the effects of probiotics on cognitive function changes in Alzheimer's disease (AD) rats, and to preliminarily explore its underlying mechanism. Methods: Ninety male rats were divided into three groups: sham-operated group, model group, and (model+probiotics) group, with 30 rats in each group. In the sham-operated group, sterile water was injected into the bilateral hippocampal CA1 regions of the rats. In the model group, Aβ1-42 was injected into the same regions. In the (model +probiotics) group, Aβ1-42 was injected into the bilateral hippocampal CA1 regions, followed by probiotic gavage. Cognitive function was evaluated in each group of rats. Immunofluorescence was used to detect changes in microglial cells (M1 and M2) in the cortical and hippocampal regions. Primary microglial cells were isolated and cultured, and the expression of IBA1 was observed using immunofluorescence, along with the measurement of phagocytosis. Results: The (model+probiotics) group exhibited significantly enhanced correct channel selection ability in the Y-maze test compared to the model group, with an increase in correct channel selection ability (P<0.05). Compared with the sham-operated group, the expression of IBA1 protein in the hippocampal tissue was significantly elevated in both the model group and the (model+probiotics) group (P<0.01), with no statistically significant difference between the model group and the (model+probiotics) group (P>0.05). Compared with the sham-operated group, the expression of M1-type microglial cells increased in the cortical and hippocampal regions of both the model group and the (model + probiotics) group (P<0.05). Compared with the model group, the (model+probiotics) group showed a significant increase in the number of M2-type microglial cells in the cortical and hippocampal regions (P<0.05), along with a decrease in the M1/M2 microglial cell ratio in these regions (P<0.05). Additionally, the phagocytic activity of microglial cells against Aβ was significantly stronger in the (model+probiotics) group than in the model group (P<0.05). There was a statistically significant difference in TH17 levels among the three groups (P<0.05), whereas no statistically significant differences were observed in Treg levels or the Th17/Treg ratio. Conclusion: Probiotics can improve spatial exploration ability and working memory capacity in rats and enhance the phagocytic function of microglial cells. The mechanism may involve inhibiting the conversion of M1-type to M2-type microglial cells.