Abstract: There is an important physico-geographic boundary line on the Qinghai-Xizang (Tibetan) Plateau. It is the Gangdisi-Nyainqentanglha range.The physico-geographical differentiation of both sides of the Gangdisi-Nyaiqentanglha range is conspicuous owing to their altitudes and latitude position Both natural zones are separated by the range, the zone of montane shrubby steppe of broad valleys and basins of South-Xizang is located on the south, the zone of alpine-steppe of the Qiangtang Plateau stretches to the north.The background of topographic configuration, climatic differentiations, hydrographical features a.nd characteristics of vegetation and agriculture of the two zones are discussed in the present paper. The boundary line of the Gang-disi-Nyainqentanglha range is compared with the important boundary line-the Qin Ling mountain-Huai He river line in Eastern China. The former on the plateau may be considered as a variety of the latter outside the plateau that has been raised to a much higher elevation.