Abstract: Ribosome is a ribonucleoprotein complex that is composed of rRNAs and proteins, and is responsible for the synthesis of polypeptide chains in all living cells. Euplotes octocarinatus is a freshwater ciliate which possesses unique regulation of gene expression. The study of the unique features of E. octocarinatus ribosomal proteins has been hampered by the lack of available information. In this study, we performed bioinformatic approach to conduct a syste-matic analysis of the CRPs of E. octocarinatus. We identified 98 genes encoding 78 different CRPs. Interestingly, 19 CRP genes are present as duplicates and, while all appear to be functional, one member of each gene pair has relatively limited expression. Compared with higher eukaryotic organisms, the ribosomal proteins eS30 and eL6 of E. octocari-natus lost ubiquitin-like domain and Ribosomal_L6e_N domain, respectively. Furthermore, the uL10 of E. octocari-natus is a basic protein. Our study lay a foundation for the future understanding of the assembling and function of ribosome in lower eukaryotic organisms.