Three femal Dechang water buffaloes were used in this study. Total DNA were extracted by bead-beating method. Primers of Met86F/Met1340R were used to amplify the 16S rRNA of archaea for the construction of library. Results showed that 99 sequences were obtained. RDP analysis showed that 94.2% sequences are classified to genus Methanobrevibacter. Based the 97% similarity, these sequences were assigned to 19 OTUs. Ninety-six sequences showed ≥97% sequence similarity to known species, three sequences had sequence similarity to known species in the range of 90% to 97%. Phylogenetic analysis indicated that 75.8% archaeal sequences in the rumen of Dechang water buffaloes belonged to SGMT clade, only 1.0% sequences belonged to RO clade. There are some sequences far from all known species on the phylogenetic tree. They may represented new species in Methanobrevibacter genu in the rumen of Dechang water buffaloes. It can be concluded that Methanobrevibacter genu is the dominant archaea in the rumen of Dechang water buffaloes. Further study should be done for the isolation of uncutured methanogens and their function analysis.