The gayal (Bos frontalis) is a very rare, semi-wild and semi-domestic bovine species. There still exist remarkable divergences on the gayal’s origin and phylogenetic status. The cytochrome b (Cyt b) gene entire sequences (1 140 bp) of 11 gayals were sequenced and analyzed. Combined with other bovine Cyt b entire sequences cited in GenBank , the phyloge-netic trees of genus Bos were reconstructed by neighbor-joining (NJ) and maximum parsimony (MP) methods with Bubalus bubalis as outgroup. Sequence analysis showed that, among 1 140 sites of Cyt b gene entire sequences of 11 gayals, 95 variable sites (8.33 % of all sites) and 6 haplotypes were found, showing abundant genetic diversity in mitochondrial Cyt b gene of the gayals. Both NJ and MP trees demonstrated that the gayals in this study were markedly divided into three em-branchments: one embranchment clustering with Bos taurus, another clustering with Bos indicus, and the third clustering with Bos gaurus. The result of phylogenetic analysis suggested that the gayal might be the domesticated form of the gaur (Bos gaurus), and a great proportion of the gayal bloodline was invaded by other bovine species.