Background: The microbiota plays an important role in host health. Although rubidium (Rb) has been used to study for depression and cancers, the interaction between microbial commensals and Rb is still unexplored. To gain the knowledge of the relationship between Rb and microbes, 51 mice receiving RbCl-based treatment and 13 untreated mice were evaluated of their characteristics and bacterial microbiome changes.Results: The 16S ribosomal RNA gene sequencing of feces showed RbCl generally maintained fecal microbial community diversity, while the shifts in fecal microbial composition were apparent after RbCl exposure for the first time. RbCl significantly enhanced the abundances of Rikenellaceae, Alistipes, Clostridium XlVa and sulfate-reducing bacteria including Deltaproteobacteria, Desulfovibrionales, Desulfovibrionaceae and Desulfovibrio. While, RbCl significantly inhibited the abundances of Tenericutes, Mollicutes, Anaeroplasmatales, Anaeroplasmataceae and Anaeroplasma lineages. Besides, with regarding to the composition of archaea, RbCl significantly enhanced the abundances of Crenarchaeota, Thermoprotei, Sulfolobales, Sulfolobaceae and Sulfolobus lineages. Conclusions: These results revealed that enrichments of Clostridium XlVa and Alistipes could affect the levels of serotonin, a critical signaling molecule of brain-gut-microbiota axis. Therefore, anticancer and anti-depressant effects of RbCl might be partly mediated by modifying brain-gut-microbiota axis.