The vulnerable eco environment and most sensitive global environmental change characterize the research area. The moisture regime is a principle factor, by which the differentiation and variance of the physical geographical environment are influenced directly. The structure, function, and spatial distribution pattern of the regional eco geographical system along the longitude is determined by the key factors of precipitation, moist coefficient/aridity, and soil moisture regime. Regional differentiation in annual or growing season (from May to September) potential evapo transpiration is obvious. The annual aridity is increased from the east to the west of the research area, although it is affected by contour microclimates. The aridity in summer and fall is less than that in winter and spring. The regional differentiation in vegetation and soil is also impacted by the moist regime. Based upon the land use structure, the research area may be divided into five land use types.