Abstract:[Objective] Propsilocerus akamusi is one of the most important insects in aquatic ecosystem, and its gut microbiota is closely related to individual growth and development, environmental adaptation, and other physiological processes. This study aimed to investigate the potential effects of antibiotic treatment on the structure and the function of gut microbiota in P. akamusi larvae. [Methods] The microbes in the gut content of P. akamusi larvae treated by rifampin were analyzed and compared by using the 16S rRNA amplicon sequencing, and the functional prediction of gut microbial genes was conducted by using Tax4Fun method. [Results] Rifampin altered the structure and the diversity of gut microbiota in P. akamusi larvae. After rifampin treatment, the relative abundance of the bacterial phylum Bacteroidota (P<0.05) and Deferribacterota (P<0.001) was up-regulated, while that of Proteobacteria and Firmicutes was down-regulated. At the genus level, treatment with rifampin resulted in a significant decrease in the relative abundance of Yersinia,Pseudomonas, and Desulfovibrio (P<0.05). At the same time, the co-occurrence network showed that the stability of the microbiota coupled with the correlation between bacterial species were significantly weakened after rifampin treatment. Additionally, the Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis predicted that genes in the gut microbiota of P. akamusi larvae were mostly involved in the genetic information processing, metabolism, and human disease. Rifampin significantly increased the expression level of genes involved in drug resistance, while decreased those participating in endocrine and metabolic disease function. [Conclusion] The above-mentioned results reveal the potential effects of rifampin on the structure and the function of the gut microbiota in P. akamusi larvae, which build a fundamental basis to further explore the essential roles of the gut microbiota in P. akamusi.