The soil microbial diversity of Tanggula Mountain Pass along the Qinghai-Tibet railway was analyzed by 16S rDNA cloning, amplified ribosomal DNA restriction analysis (ARDRA), and sequence homology comparisons. Among 90 positive clones in the 16S rDNA library of microorganisms, 23 OTUs (Operational Taxonomic Units) were identified based on the similarity of the ARDRA banding profiles. Sequence analysis revealed diverse phyla of bacteria in the 16S rDNA library, which consisted of alpha, beta, delta subclasses of the Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Acidobacteria and Planctomycetes. The dominant group was alpha-Proteobacteria (33.3% of the total clones), and the most dominant genus was Bradyrhizobium. More than 22.2% of the total clones showed high similarity to uncultured bacteria. The results suggest that the soil microbial diversity is abundant in this area.