Abstract: Hyriopsis cumingii, an endemic species of China, is also an important economic shellfish and is widely used in the pearl farming industry. In order to better understand the role of CPEB1 gene in meiosis of H. cumingii oocytes and its function in gonadal development of H. cumingii, we cloned the full-length CPEB1 cDNA (2 527 bp) and analyzed its structural features. Tissue expression patterns were examined via RT-qPCR, with gene localization determined by in situ hybridization. Two RNA interference strands (G1, G2) were designed for gene silencing, coupled with flow cytometry for oocyte cycle analysis and downstream gene (P90rsk, CDC25B) expression profiling. The CPEB1 cDNA contains a 1 971 bp ORF encoding 657 amino acids. RT-qPCR revealed significantly higher CPEB1 expression in female tissues (except liver) versus males, with ovarian expression exceeding testicular levels by >2 000-fold. In situ hybridization demonstrated strong cytoplasmic signals in female ovarian oocytes of the experimental group compared to negative controls, while no significant positive signal observed in the male testis experimental group compared to the control group. RNAi strand G2 exhibited maximal interference efficiency (91.98% in females vs. 23.46% in males). Post-interference, female P90rsk and CDC25B expression decreased by 44.14% and 44%, respectively, while male CDC25B declined by 78.19%with no significant P90rsk changes. Compared with the control group, the proportion of oocytes in G1 phase increased and decreased in S phase, and there was no significant change in G2 phase, suggesting that the interference of CPEB1 gene may hinder the normal transition of oocytes from G1 phase to S phase, indicating that CPEB1 gene may play a role in the process of oocyte meiosis. It affects the ovarian development of the H. cumingii, which is of great significance for exploring the sex differentiation of the H. cumingii.The identified sexually dimorphic regulatory mechanisms provide theoretical support for gender-controlled breeding and direct applications in pearl aquaculture optimization.