[Aim]  To characterize the composition and potential functions of the gut microbiota of two major leaf beetle pests, Plagiodera versicolora and Humba cyanicollis, in tea plantation ecosystems. [Methods]  Microbial amplicon sequencing was used to analyze gut microbiota community structure and predict the functions of the gut bacteria and fungi of both species. [Results]  The gut bacterial communities of both species were dominated by Proteobacteria and Firmicutes at the phylum level, with key genera including Enterobacter, endosymbionts, Spiroplasma, and Lactococcus. The fungal communities were primarily composed of Ascomycota and Basidiomycota, dominated by Cladosporium, Fusarium, Penicillium, Aspergillus, and Didymella. Although the relative abundance of major microbial taxa differed between beetle species, there were no significant differences in alpha diversity. Although the bacterial community structure (beta-diversity) was significantly different between species (P=0.001), fungal community structure was not. A core microbiota, consisting of shared bacterial and fungal taxa, formed the majority of the gut microbial community in both species. Furthermore, functional prediction indicated minimal differences in the metabolic potential of both bacteria and fungi between the two species. [Conclusion]  These findings describe the structure and potential functions of the gut microbiota of P. versicolora and H. cyanicollis, providing a valuable foundation for developing targeted biological control strategies for these coleopteran tea pests.