A series of gorges on the lower reaches of the Yarlung Zangbo River is like an enormous crevice splitting the southeastern Qinghai-Xizang (Tibet)Plateau to create a passage through which warm, wet air flow from the Indian Ocean reaches the inner part of the plateau. This moisture passage was mainly strengthened after the Pleistocene epoch in the Quaternary period and has played a major role in affecting the beginning date of the rainy season and the amount of the plateau’s rainfall. It has also served as a corridor for the living things on the southern and the northern sides of the Himalayas to mingle with each other. The region along this passage is abundant in evidences of species of differentiation, variation and biological division. Also the passage has provided a favorable environment for human beings and affected natural phenomena there. A series of gorges on the lower reaches of the Yarlung Zangbo River is like an enormous crevice splitting the southeastern Qinghai-Xizang (Tibet) Plateau to create a passage through which warm, wet air flow from the Indian Ocean reaches the inner part of the plateau This moisture passage was mainly strengthened after the Pleistocene epoch in the Quaternary period and has played a major role in affecting the beginning date of the rainy season and the amount of the plateau’s rainfall. It has also served as a corridor for the living things on the southern and the northern sides of the Himalayas to mingle with each other. The region along abundant this evidences of species of differentiation, variation and biological division. Also the passage has provided a favorable environment for human beings and affected natural phenomena there .