Abstract: In order to explore the classification status and genetic diversity of Tibet yak at the molecular level, the cytb gene sequences of Tibet yaks were determined; its sequence polymorphism was analyzed; and the molecular phylogenetic tree was constructed for 110 yaks from 11 groups (Jiali, Sangsang, Sangri, Gongbujiangda, Sibu, Pali, Kangbu, Jiangda, Leiwuqi, Dingqing, Baqing yak). The results showed that the size of cytochrome b gene sequences of 110 yaks are 1 140 bp. 53 haplotypes were identified, 49 haplotypes were newly discovered, 14 SNPs loci among 110 sequences were detected, nucleotide mutation types included conversion and transversion, no insertions and deletions, the main mutations was synonymous mutations, which indicated that Tibetan yaks had abundant genetic diversity. 11 species or groups of Tibet yak can be divided into 5 strains:Pali,Jiangda,Baqing,Sangri,Leiwuqi yak.