Abstract: In order to further elucidate the structurefunction relationship of RPS3 which has multifunction in vivo and to reveal the possibility of its CDS as a phylogenetic marker, the RPS3 cDNA (GenBank accession No: DQ660373) was cloned using bioinformatics, RT-PCR and 3′-RACE methods; and its expression profile was researched with semiquantitative RT-PCR. Sequence analyses showed that the full ORF is 732 bp, encoding a polypeptide of 243 amino acids which includes the ribosomal protein S3 signature. The phylogenetic tree demonstrated similar topology with the zoology. Semiquantitative RT-PCR analyses showed that the expression level is the highest in heart and the lowest in liver, and there are no significant difference among other tissues. With the age increasing, the expression level gradually decreases and becomes steady in pigs older than three months. The results made clear that the coding sequence of RPS3 fits to construct phylogenetic tree among species and its expression at mRNA level is related to growth and metabolism