[Aim] Leptocybe invasa is an important invasive forestry pest. We examined the host adaptation mechanism of L. invasa by studying the influence of different hosts on its bacterial community composition and diversity. [Method] Illumina HiSeq high-throughput sequencing was used to analyze the V3+V4 region of bacterial 16S rDNA from L. invasa adult females, which were fed on DH201-2 (Eucalyptus grandis×E. tereticornis) and E. exserta. [Result] A total of 273461 valid reads were obtained from the 16S rDNA sequence library of the two samples, and 230 bacterial operational taxonomic units were identified using a 97% similarity clustering analysis, of which 206 were identified from DH201-2 and 171 from E. exserta. Adult females fed on DH201-2 had more bacterial species and higher bacterial community richness but lower diversity. Female adults of L. invasa fed on E. exserta had fewer bacterial species and lower bacterial community richness but higher diversity. Fourteen phyla, 24 classes, 41 orders, 73 families, 123 genera, were identified among the bacteria in the two samples. The dominant bacterial phylum in both populations was Proteobacteria, with a relative abundance of >90%. The dominant bacterial genus in L. invasa feeding on DH201-2 was Rickettsia, accounting for 93.11%, reflecting low diversity, and the relative abundance of Rickettsia in individuals feeding on E. exserta was 73.61%, showing higher species diversity. [Conclusion] The richness and diversity of bacterial communities significantly differed in L. invasa fed on different host plants, suggesting that host plants can affect the composition and structure of bacteria in the larvae of L. invasa.