Abstract: As a coprotein of DNA polymerase δ, proliferating cell nuclear antigen (PCNA) plays an important role in the process of DNA replication. There is a stage of vigorous cell proliferation during the ovarian development in Metapenaeus affinis, but little attention has been paid to its molecular mechanism. In this study, we applied rapid amplification of cDNA ends (RACE) technique to obtain the full length cDNA sequences of PCNA in M. affinis (MaPCNA), and analyzed the expression of MaPCNA related to ovarian development by real-time fluorescent quantitative PCR (qRT-PCR). The total length of MaPCNA was 1 144 bp, including 140 bp of 5' untranslated region, 221 bp of 3' untranslated region and 783 bp ORF encoding 260 amino acids. The molecular mass of MaPCNA protein was 28.82 kD and the theoretical isoelectric point was 4.5. The protein homology analysis shows that MaPCNA had high homology with other crustaceans. The result of tissue expression shows that Ma-PCNA was expressed in all tested tissues, with the highest expression in ovary (P<0.05). The expression of MaPCNA in ovary at different developmental stages showed significant changes (P<0.05), increasing from stage I to stage III gradually, decreasing significantly and then tending to be stable. The expression of MaPCNA showed a regular change trend at different larval developmental stages. The expression level of MaPCNA was the highest in oosperm, then began to decline, and became stable from the Nauplius VI. The results suggest that PCNA may play an important role in the ovarian development of M. affinis.