Objective To evaluate the effect of probiotics on cognitive and emotional relief in patients with Alzheimer's disease or cognitive impairment. Methods Seven Chinese and English databases including PubMed and CNKI were searched for randomized controlled trials on improving cognition or emotion by taking probiotics published before May 1, 2021. According to the inclusion criteria and exclusion criteria, the included literatures were screened and evaluated. Then Revman 5.3 was used to analyze the extracted data. Results A total of 17 articles were included in the study, of which 9 were of high quality. Meta analysis showed that probiotics could alleviate the course of cognitive impairment or make the mood optimistic (RR=2.07, 95% CI［1.79,2.39］, I2=79%), the difference was statistically significant (P＜0.05). Conclusion Probiotics have a positive effect on cognitive function in patients with cognitive impairment.