Plutella xylostella, a globally economically important pest of cruciferous crops, has varying degrees of resistance to almost all insecticides. Insect gut microbiotas have a variety of physiological functions, and recent studies have shown that they have some potential connection with insecticide resistance. Here, we use metagenomics to analyze the differences in gut microbiota among 5 different populations of P. xylostella resistant to chlorantraniliprole. Differential gene expression was enriched in various metabolic pathways including carbohydrate metabolism, amino acid metabolism, energy metabolism, metabolism of cofactors and vitamins, nucleotide metabolism and so on. Proteobacteria was the dominate phyla, and the relative abundance of common dominant genera in the treated group (CL, Bt, and BtCL) was higher than that in susceptible controls. We successfully isolated 15 species of bacteria, in which the Enterobacter hormaechei was associated with enhanced insecticide resistance. The population we isolated can metabolize chlorantraniliprole in vitro, with a metabolic rate of 34.8 % within 4 days. Our work advances understanding of the evolution of insecticide resistance and lays a foundation for the further exploration of symbiotic microbial associations of lepidopteran insects and their ecological consequences.