[Aim]  Gut microbes play an important role in the development of pest resistance. Spodoptera litura is a widespread polyphagous pest species that is becoming increasingly resistant to pesticides. To determine the relationship between gut microbes and host resistance, we compared gut microbial diversity between bromoflumizamide-susceptible and bromoflumizamide-resistant populations of S. litura. [Methods]  DNA samples of gut microorganisms were taken from S. litura with intermediate levels of bromoflumizamide resistance and susceptibility. Amplicon sequencing of the 16S V3-V4 region was carried out using high-throughput sequencing technology to optimize the OTUs based on 97% similarity and determine microbe species abundance, gut microorganism composition and structure, α diversity, and β diversity. [Results]  Total microbiome sequencing yielded 1 208 279 sequences which were optimally clustered into 529 OTUs containing 22 phyla, 44 classes, 84 orders, 138 families, and 207 genera. At the genus level, there were 62 endemic genera in the bromoflumizamide-susceptible population and 50 endemic genera in the bromoflumizamide-resistant population. The two populations shared 95 genera. There were significant differences in the composition of the intestinal flora between the two strains (P<0.05). Erysipelatoclostridium dominated the microbiome of the bromoflumizamide-resistant population, whereas Enterococcus was the dominant microbiome in the bromoflumizamide-susceptible population, with relative abundances of 57.24% and 47.71%, respectively. Diversity analysis showed that the intestinal microbial community of the bromoflumizamide-resistant population of S. litura had the highest species abundance. In contrast, the bromoflumizamide- susceptible S. litura population had a higher species richness and consistency. [Conclusion]  There was a significant difference in the microbial community composition between the bromoflumizamide-susceptible and bromoflumizamide-resistant populations. The bromoflumizamide-resistent population of S. litura exhibited a more complex gut microbome composition, while the bromoflumizamide-susceptible S. litura population exhibited a more stable flora composition. In this paper, we explored the relationship between insect resistance and gut microorganism diversity. Our findings provide a new perspective for the development of novel pesticides and lay a foundation for further research into the mechanisms of resistance in S. litura.