Abstract: 【Objective】 Cloned the open reading frame(ORF) of peroxiredoxin gene(EsPrx) of Eriocheir sinensis, and analyzed the tissue expression characteristics of EsPrx gene and its expression under bacterial infection, which provided reference for the study of innate immunity and disease resistance mechanism of E. sinensis.【Method】 The EsPrx gene was cloned by combining RT-PCR with transcriptome sequence alignment analysis. Bioinformatics analysis was performed using online software such as DNAStar, ClustalW, ExPASy, TMHMM Server v.2.0, SignalP 5.0, and NetPhos 3.1 Server. The tissue expression characteristics of the EsPrx gene and its expression in the presence of Vibrio anguillarum infection were detected by real-time fluorescence quantitative PCR.【Result】 The ORF of EsPrx gene was 597 bp, encoding a total of 198 amino acid residues, and it contained two domains specific to Prx(FYPLDFTFVCPTEI and GEVCPA). The molecular formula of EsPrx protein was C₉₉₄H₁₅₄₄N₂₅₈O₂₉₃S₈, with a molecular weight of 22.05 kDa and a theoretical isoelectric point(pI) of 5.67. Without transmembrane domain and signal peptide, it was a non-secretory protein. The amino acid sequence of EsPrx was highly homologous with the Prx amino acid sequence of Eurypanopeus depressus, Scylla paramamosain and Portunustri tuberculatus, with the corresponding similarities of 89%, 89% and 88%, respectively. The phylogenetic tree constructed based on the similarity of Prx amino acid sequence showed that the amino acid sequence of EsPrx was first clustered with the Prx amino acid sequence of S. paramamosain, E. depressus and Penaeus vannamei, and then clustered with the 2-Cys Prx amino acid sequence of other animals, confirming that the EsPrx gene belonged to the undifferentiated Prx gene, namely, Prx1/2 gene. The EsPrx gene was widely expressed in various tissues of E. sinensis, and the relative expression level of EsPrx gene in hepatopancreas was the highest, which was extremely significantly higher than that in other tissues(P<0.01). The expression of EsPrx gene was greatly different at different time points of Vibrio anguillarum infection, and its relative expression was significantly increased 6-24 h after infection(P<0.05), and then rapidly decreased to normal level.【Conclusion】 EsPrx gene is an undifferentiated Prx1/2 gene of crustacean, which is highly expressed in hepatopancreas of E. sinensis, and participates in the anti-oxidative stress response of V.anguillarum infection, that is, plays an important role in the resistance process.