Abstract  [Aim]  Thioredoxin peroxidases (TPX) plays an important role in protecting insects against oxidative stress. This study aims to provide a foundation for exploring the physiological function of the TPX gene in A. ipsilon by identifying the TPX sequence in A. ipsilon and determining the antioxidative ability of the protein encoded by the gene. The study will also investigate the expression profile of the TPX gene during different developmental stages, in various tissues, and in response to stress induced by three insecticides (lambda-cyhalothrin, phoxim, and chlorantraniliprole). [Methods]  The TPX gene was identified within the A. ipsilon transcriptome using a homology search-based method. The recombinant protein was expressed in Escherichia coli and its antioxidative ability was analyzed. The expression profile of the TPX gene was determined using reverse transcription quantitative PCR. A commercial kit was used to test the H₂O₂ content of larvae. [Results]  A cDNA sequence (designated AiTPX1) encoding putative TPX was identified from the A. ipsilon transcriptome. AiTPX1 encoded a protein belonging to the 2-Cys family based on its structural features and the results of the phylogenetic analysis. The recombinant AiTPX1 protein was successfully expressed in E. coli, significantly improving the tolerance of E. coli cells to oxidative stress. The mRNA of AiTPX1 was detected in all A. ipsilon developmental stages and tissues tested in this study, with the highest levels found in the pupal stage and larval midgut. After treatment with LC₅₀ concentrations of lambda-cyhalothrin, phoxim, and chlorantraniliprole, the H₂O₂ content of larvae was significantly increased and there was notable upregulation of AiTPX1 at the transcriptional level. [Conclusion]  AiTPX1 may enhance the tolerance of A. ipsilon larvae to lambda-cyhalothrin, phoxim, and chlorantraniliprole by alleviating oxidative stress induced by exposure to the three insecticides.