Abstract: In arid area of northwest China, the NaF and KF are extensively distributed in the natural water, such as rivers, lakes and groundwater. From mountains to silt plain along with the formation, runoff and disappear of inland rivers, the distributing regularity of F^- can be markedly divided into three hydrochemical zones: drench and dissolution-runoff zone, runoff-evaporation zone, dissolution-evaporation zone. In the low-lying land and desertification edge with Lacustrine sediments deposited from Cretaceous and lower Pleistocene of Quaternary period, the contains of F^- in groundwater was high with the vertical distributing pattern of larger in lower and letter in upper. There are close relationship between high F^- and the hydro-chemical characteristics. Generally, in the alkali water with lower contains of So₄^2- such as Cl稨CO₃-Na or HCO₃-Na types, the F^- can be easily dissolved and rich in water. The arid climatic conditions, rich source of Fluorine and relatively close hydrological environment provide the advantage of F^- to dissolution, transformation and rich in some regions.