Altitude of the plateau may affect the composition and functional diversity of animal gut microbiota. However, the specific effects of altitude on the composition, community structure, and function of the host's gut microbiota, as well as how these effects, through interactions between microbial metabolic products (e.g., SCFAs) and microbial diversity, support host adaptation to high-altitude environments, remain unclear. This study investigates the variations of gut microbial community structure and function in plateau pikas (Ochotona curzoniae) along altitude on Qinghai-Tibetan Plateau. Cecum contents were analyzed using 16S rRNA sequencing and short-chain fatty acid (SCFA) content analyses to explore the structure, function and metabolic characteristics gut microbiota across different altitudes. As altitude increases, pikas' gut microbiota diversity significantly decreased, SCFA levels did not significantly change, while both diversity and complexity of the microbiota co-occurrence networks significantly decreased. The microbial community shifted toward better suited to high-altitude environments, as significantly increased in Bacteroidetes abundance but decreased in Firmicutes abundance. The microbial community assembly process became more deterministic, and KEGG analysis revealed the upregulation of metabolic, genetic information processing, and organismal system pathways. These results indicated that the gut microbiota diversity and complexity decreased in plateau pikas with increasing altitude, along with the upregulation of key metabolic pathways, as well as the stability of SCFA levels which reflecting balanced supply-demand relationships, contribute to adaptation of high-altitude environments. These findings reveal the substantial impact of altitude on the gut microbiota of a small mammal inhabiting the plateau, providing new insights into its adaptation mechanisms to high-altitude environments.