Abstract:Abstract: [Objective] In order to investigated composition and diversity of bacterial in a cold sulfur spring in Xinjiang faulting zone. [Methods] Environmental total DNA was directly extracted from the water of the No.10 cold sulfur spring. The 16S rRNA genes were amplified from the total DNA by PCR with bacteria-speci?c primers and construction a clone library. Positive clones were randomly selected from the library and identified by restriction fragment length polymorphism (RFLP). The unique RFLP pattern corresponded sequences were sequenced, BLAST and then constructed phylogenetic tree. [Result] In total, 228 positive clones were screened and grouped into 33 Operational Taxonomic Units (OTUs). The clone coverage C value was 92%.33 Operational Taxonomic Units were divided into 3 phyla with Blast analysis and RDP classifer: Proteobacteria, Bacteroidetes, and Firmicutes. Proteobacteria (98%) was the absolutely dominant group, of which 20% of the clones were highly related to the known photoautotrophic and chemoautotrophic bacteria (> 97 % sequence similarity). Besides, 64% of the clones showed less than 96% of sequence similarity with sequence deposited in GenBank database, of them 54% sequences were affiliated to genus Legionella spp. [Conclusion] Bacterial diversity in No.10 cold sulfur spring was low, but maybe have a diversity of novel species and lineages. In addition, large number of novel species of Legionella were detected in the spring water may suggest the water potentially a source of Legionnaires disease and may constitute a menace to the health of human and livestock that lived down the spring.