Abstract: Cytochrome C oxidase (COX) is a member of the heme-copper oxidase superfamily, which is a terminal oxidase of eukaryotic mitochondrial intima and aerobic bacterial cell membrane respiratory electron transport chain, and is closely related to the synthesis of ATP. The COX7C gene is a subunit of the cytochrome C oxidase. In this study, the open reading frame COX7C gene of Plutella xylostella was cloned and sequenced, which includes 213 bp nucleotide. The phylogenetic tree analysis showed that COX7C was not highly conserved between the same order insects. The expression levels of COX7C in the third instar larvae of chlorpyrifos-, fipronil-resistant and susceptible strains were analyzed by qPCR. The results showed that COX7C was expressed in all three strains, and the expression level in the fipronil-resistant strain was significantly higher than that in SS, indicating that it might be involved in the process of detoxification of fipronil in P. xylostella. This study only conducted a preliminary study of COX7C in the P.xylostella, and a foundation for further research on the function of COX7C in the future.