Abstract: We screened the ubiquitin/ribosomal S27 fusion protein (PmUbS27) from hepatopancreas transcriptome data of Penaeus monodon and cloned the full-length PmUbS27 cDNA sequence by SMART-RACE technology. Besides, we studied the expression of ovaries of PmUbS27 gene at different developmental stages and in different tissues by real-time quantitative detection. The PmUbS27 cDNA was 514 base pairs (bp) long, containing a 3′-UTR of 39 nucleotides and a 465 bp open reading frame (ORF) encoding a 154 amino acid polypeptide. The PmUbS27 protein contained the conserved Ub domain and ribosome structure. The DNA-cloned gene sequence consisted of four exons and three introns. PmUbS27 mRNA was ubiquitously detected in all tested tissues, comparatively high in the ovary, hepatopancreas and lymph. The expression level of PmUbS27 mRNA was significantly higher in ovary at Stage Ⅱ and Stage Ⅴ (P < 0.05). It is showed that PmUbS27 had an important role in oogenesis of P. monodon.