Tibetan sheep is one of the three primitive sheep breeds (Mongolian sheep, Tibetan sheep, and Kazakh sheep) in China. It is also one of the typical herbivores in the Qinghai-Tibet Plateau of China. It lives at an altitude of more than 3,000m. Grazing is carried out throughout the year, and nutrition is mainly obtained by uptaking natural grass. Tibetan sheep have a wide range of adaptation to agro-ecological environment, which provides a good model for studying the genetic mechanism of the adaptive response of livestock to extreme environments. The number of Tibetan sheep is huge and widely distributed. They are concentrated in arid and semi-arid areas in northwestern and southeastern of Tibet.Tibetan sheep is one of representative herbivores in northwestern China, with more than 23 million individuals distributed throughout the Qinghai-Tibet plateau (statistics in 2008) . After the long course of evolutionary history, Tibetan sheep has been adapted to the harsh environment and plays an irreplaceable role in economic and social development for local people. Genomic reconstruction results indicate that Tibetan sheep was originated from northern Chinese ancient sheep ∼3100 years ago and achieved the divergence ∼2500 years ago. Since then, a subgroup of Tibetan sheep continued to southwest expand and reached to the central Tibet area ∼1300 years ago, while the rest of them colonized different areas of Qinghai and gradually evolved into different breeds depending on geographic conditions.