【英文摘要】With the recognization of the impact process and mechanism of water-saving rebuilding of northwestern inland arid irrigated areas on regional water cycle and its effect on ecological environment as the main clue, and quantitative simulation of regional water cycle as the emphasis, using GIS,RS and the distributed model, the aim is to understand the impact mechanism and process of irrigated areas water-saving rebuilding on the regional water cycle and ecological environment, to set up the response model between irrigation water use efficiency and water-saving rebuilding, to establish the appraisal index system of the hydrological and environmental effect of water-saving rebuilding,and also to develop the irrigated area water-saving rebuilding module and the threshold of irrigation water use efficiency that are ecologically heathy and environmentally friendly. Additionally, we try to answer how the water-saving rebuilding in northwestern inland arid irrigated areas quantitatively affects irrigation water use effeciency, what would happen to the groundwater table and ecological environment of irrigated areas in lower reach when water-saving rebuilding has applied in upper reach and how to evaluate it, how to establish reasonable water-saving rebuilding module respectively in upper, middle and lower reach so that the whole river basin's ecological environment goes in sound cycle and other questions, the purpose of which is to provide scientific basis and decision support for the water-saving rebuilding of large and middle irrigated areas in the northwest and to accelerate the innovation and development of water science and ecological science.