The arid land in Western China refers to the vast areas in the west of He[an Mountain and the north of Kunlun Mountain.The total area is 2 500 000 km.Studying and improving of eco-environment of the arid land in that region has significant meaning to the implementation of the national strategy and policy in the speeding up the development in that region, the maintenance of the social order and the territory integration of China.The item studies the scientific problems of the eco-environmental evolution of the arid 1and,the ecologica1 security mechanism of oasis,the degeneration mechanism of eco-environment,and the control．adjustment and management of the ecosystem.On the aspect of chronology,it studies the eco-environmental evolution over 10 000 year,and quantitatively studies the influence of the natural effect and human activity;On space-structure,it studies the structure and function of ecosystem from ecological system,landscape,and regional scale,and the coupling mechanism of the mountainous region,oasis and desert ecosystem and regional characteristics of ecosystem ;on the other hand,the coupling of space and chronology is also studied,it comprehensively evaluates quality and analyzes the evolutionary trend of eco-environment.It pays more attention to studies of significant problems in the developing process of western region of China.The objective of the item is to define the dynamic capacity,and security threshold and ecological water demand in the arid land of West China. The objective also puts forward the appropriate developing scale,the technical methods of the ecological restoration and rebuilding,the prevention and cure countermeasure of the eco-environmental disaster in the arid land.Meantime,the map of regional ecological distribution of the area is made,the eco-environmenta1 evolution mode1,the eco-environmental information system and the policy support system are established.The basic frame of the arid 1and eco-environmental theory is set.