Background: Bisphenol A (BPA) is an endocrine-disrupting chemical (EDC) with a weak estrogen-like activity in fish that is found ubiquitously in aquatic environments. However, there has been little study about BPA on the endocrine disrupting effects of crab. In the present study, cDNA of vasa was cloned and characterized in the Charybdis japonica. Histological structures of testis and expression patterns of vasa gene in the testis of C. japonica after treatment with BPA were investigated. Results: The cDNA of vasa is composed of 3051 bp with a 2166 bp open reading frame encoding 721 AA. The deduced amino acid sequence contained eight conserved domains of the DEAD-box protein family. The tissue distribution showed that vasa mRNA was specifically expressed in ovary and testis. Histologically, the sperm cells were decreased in number and an acellular zone was seen in the testis. The transcript level of vasa gradually increased with a significant difference between the experimental and control groups. After BPA exposure with 0.50 and 1.00 mg/L for 1,3, 6 and 9 d, the expression levels of vasa increased. Conclusion: These findings suggest that BPA can increase the expression level of vasa mRNA and influence the development of the testis in C. japonica.