Abstract: Ribosomal smallsubunit RNA gene sequence of ten Chinese Theileria strains infective to cattle, including four isolates of Theileria annulata, three isolates of T. sergenti and three isolates of T. sinensis, collected in the protozoon resource library at the centerconservation of strain in China veterinary microbion, were cloned and analyzed and then the phylogenetic trees were constructed based on 18S rRNA sequence of the Chinese isolates as well as other species of Theileria available in GenBank. The result indicated that the length of the 18S rRNA gene of all Theileria species involved in this study were varied between 1 740-1 890 bp and Chinese isolates of three Theileria isolates were located in the different phylogenetic branch, moreover, the percent identities of the different isolates in species were much higher than among species. The results were basically consistent with traditional classification as well as molecular classification based on 18S rRNA gene sequence for the bovine Theileria. This study will provide a foundation for PCR detected method for bovine theileriosis.