Rr 190.70 p-602 n primers were used to amplify the rOmpA gene fragment of prototype strains (Rickettsia sibirica 246 strain and R. parkeri) and Chinese strains (BJ-90, Ha-91 and HLJ-054) of spotted fever group rickettsiae (SFGR). The PCR products were cloned into pGEM-T vector respectively and sequenced by Sanger's dideoxy method. The sequences of the tested strains were compared with the corresponding regions of prototype and reference strains of SFGR. The results showed that the homology of rOmpA gene fragments of prototype strains varied from 90.06%-96.62% in nucleotide and 83.05%-94.35% in putative amino acid respectively. Compared Chinese strains with prototype and reference strains of SFGR, it was found that the homology of BJ-90 strain and Ha-91 strain with R. sibirica 246 strain was the highest in nucleotide (99.06% and 98.31%, respectively) and in putative amino acid (98.87% and 96.61%, respectively), whereas HL-93 strain and HLJ-054 strain showed higher homology with R. japonica (96.62% and 95.68% in nucleotide, respectively) than others. Among all the Chinese strains, the homology between BJ-90 strain and Ha-91 strain was the highest, 99.25% in uncleotide and 97.74% in putative amino acid. The homology of nucleotide and putative amino acid between HL-93 strain and HLJ-054 strain was 98.12% and 94.92% respectively. The above results indicated that all SFGR so far isolated from different sources seem to be identical or closely related to R. sibirica, except for HL-93 and HLJ-054 strains, which could be considered as new members of SFGR.