Yaks belong to the genus Bos and may closely related to bison than to the other members of its designated genus. They are a typical species living in high altitude throughout the Himalayan region of the Indian subcontinent, the Tibetan Plateau, Northern Myanmar, Yunnan, Sichuan and as far north as Mongolia and Siberia. Most of the domestic yaks (Bos grunniens) are distributed in the Qinghai- Tibet Plateau of china, accounting for 95% over across the world. It is descended from the wild yak (Bos mutus) and has adopt to high altitude well after one and five million years of evolution such as larger lungs, heart and greater capacity for transporting oxygen through their blood. To adopt the cold and feed shortage, they have a thick layer of subcutaneous fat and large omasum to ferment feed longer to extract more nutrients. As indispensable resource of Tibetan people, domesticated yaks provide milk and meat for living, their dried droppings for fuel, as well as their skin and hair for shelter and clothing. In addition, it maintains many original characters and qualities. The domestic yak is an ideal model animal for high altitude adaption research.