PA28α can activate the latent 20S proteasome together with PA28α, playing an important role in th e processing of MHC class I antigen. PMSE1 gene encoding this activator has been characterized and documented in mammals, whereas, few reported among piscine. I n the present study, two pairs of primer were designed and synthesised according to the fulllength cDNA sequence of proteasome activator PA28α subunit which we had found in common carp. Using PCR two specific gene fragme nts of PA28α subunit were amplified from total genomic DNA extr acted from the spleen of common, PCR products cloned into pMD18T vector. The r ecombinant plasmids were verified by sequencing. The PA28α subu nit gene (PSME1) of common carp had been successfully cloned. The sequence resul ts were analysized with DNAStar, DNAMAN and BLAST software. Result indicated tha t carp PSME1 gene encompassed 3 602 nucleotides, 11 exons, 10 introns, which was very similar to the known PSME1 genes of other species with the same exon/intro n arrangement. Three forms are shown at intron/exon boundaries of carp PSME1 gen e, exon 5/intron 5 boundary belongs to class 1 (GAA/G), exon 8/intron 8 boundary belongs to class 2 (TCC/AA), the rest belong to class 0. The splice sites have been well conserved through evolution, and observe the regulation of GTAG comp letely. A phylogenetic analysis using PA28α and PA28α protein sequences from the GenBank verifies the presumed orthologous re lationships of the carp gene to their mammalian counterparts, and reveales a clo ser relationship between carp PA28α and zebrafish PA28α than between carp PA28α and mammalian PA28α. Comparing with human, pig, mouse, zebrafish, the structure of carp PMS E1 gene has been also well conserved through evolution. The base number of all e xons is almost stable, althongh few introns (introns 1, 5, 7 in carp; introns 1, 4, 7, 8 in zebrafish) more variable than other three mammals, especially，the b ase number of intron 8 in zebrafish PSME1 gene. Our studies have demonstrated th e carp PMSE1 gene, moreover, we have done a further work on the distinctions of PMSE1 genes among different species. However, further extensive study on this ki nds of subunit genes will be necessary for more information about their molecula r properties and functions. Key words:Cyprinus carpio〖WTB1〗；PA28α enomic DNA clone；sequence analysis