The phenylalanyl-tRNA synthase alpha subunit(pheS) gene sequences and 16S rRNA gene sequences of representative strains of 5 species and 4 subspecies from Lactobacillus casei group were analyzed by phylogenic method.The feasibility of the pheS gene sequences for species identification of the Lactobacillus casei group was studied.Results showed that the interspecies divergence of pheS gene sequences was between 6.8%~34% and the highest intra-species divergence could reach 3%.The discriminatory power of pheS gene sequences was higher than that of 16S rRNA gene sequences,the pheS gene sequences analysis could be an important tool in species identification in the Lactobacillus casei group.