In this study, the parATth gene mutant, ΔparATth, was generated by deleting the gene in Thermus thermophilus HB27 and were subjected to phenotype analysis with respect to chromosome replication and segregation. The results showed that in the ΔparATth mutant, the cell growth, cell division, cell morphology were not apparently affected. And, the chromosome copy number was not changed in the mutant and the chromosomal bulk DNA segregation was not impeded either. However, the subcelluar localization of the chromosomal origin (oriC) was randomly localized in the mutant cells instead of the polar localization pattern in the wild type cells. Therefore, in T. thermophilus HB27, the parATth gene is not critical for the chromosomal bulk DNA segregation, however, it might be involved in the chromosomal origin region localization and segregation.