Many bacteria colonized in the horse semen affect quality of the sperm and some may cause infection in the mare reproductive tract and infertility of susceptible mare. This study was initiated to determine the prevalence of bacteria in testes of Jeju horses by determining rRNA sequence. The samples were swabed from the testes of nine Jeju horses (aged from 8 to 12 months after birth). Bacteria isolated from testes were identified by 16S rDNA sequencing. 1.6-kbp PCR products for 16S rRNA coding region were obtained using the universal primers. The PCR products were further purified and sequenced. Maximum similar species were found by BLAST search in the GenBank DNA database. BLAST results showed that the sequences were similar to those of Acinetobacter sp (A. schindleri, A. ursingii)., Bacillus cereus, Corynebacterium glutamicum, Escherichia coli, Gamma proteobacterium, Micrococcus luteus, Pseudomonas mendocina, Shigella sonnei, Sphingomonas sp., Staphylococcus sp (S. cohnii, S. saprophyticus, S. xylosus)., and Stenotrophomonas maltophilia. DNA sequences for 16S rRNA is provided useful informations for species identification of pathogenic microorganisms for the reproductive organs in horses.