To investigate the role of the vasa gene in gonadal development of the triangle sail mussel （Hyriopsis cumingii）， techniques including quantitative real-time PCR （qRT-PCR） and in situ hybridization were employed to analyze the structural characteristics and spatiotemporal expression patterns of the vasa gene in male and female tissues， as well as during early and mature developmental stages of testes and ovaries. The results revealed that the vasa gene cDNA consisted of 4 673 bp， encoding 808 amino acids， containing two functional domains （DEXDc and HELICc） and nine conserved motifs characteristic of the DEAD-box protein family. The vasa gene exhibited significantly higher expression in ovaries and testes compared to other tissues （P<0.05）. During early gonadal development， its expression showed an initial increase followed by a decline， reaching significant elevation at 6 months of age with marked differences compared to other age groups （P<0.05）. In mid-to-late gonadal development， vasa expression displayed a progressive upward trend， with significantly higher levels in females than in males （P<0.01）. In situ hybridization localized vasa expression to oocytes， spermatogonia， spermatocytes， sperm cells， follicle walls， as well as primordial germ cells and follicular cells in juvenile gonads. This study suggests that the vasa gene participates in gonadal development in H. cumingii， potentially regulating primordial germ cell proliferation and gamete meiosis， serving as a putative regulatory factor in gametogenesis， and playing crucial roles in maintaining testicular/ovarian and germ cell development. These findings provide theoretical insights for research on gonadal development， gametogenesis， and monosex breeding techniques in H. cumingii.