Abstract: Loess hilly region is one of the most serious water and soil loss areas in China.This paper is the primary design and application study on the ecological environment monitoring system.It could provide the helps and information for the managing and deciding departments such as agriculture,forest,land,and water conservation.It is also the experiment and demonstration of Gansu Province's ecological environmental investigation and monitor in large scale and high speed.Now a lot of works have been carried through.The basic background data have been collected and digitalized.Most of the satellite images interpretation works have been finished and a lot of monitoring results have been calculated.In the near ten years,the land-use and land-cover in four counties of Dingxi,Gansu province changed markedly.The most distinctly increasing types are vegetable land and fruit land which increased by 275% and 164% in order.It shows that the agricultural industrial structure of the region has been adjusted in high degree and has transformed from the single grain production to the combination of grain and economical crop production.The bare land decreased markedly with more than sixty percent,which shows that the wasteland has been developed in high degree.Because the water and soil conservation and the returning crop plot to forest projects have been popularized widely,the mixed forest and shelter forest increased by 43% and 46%.The city,town,and traffic areas increased by 34%,13%,and 21% respectively,which roots in the ecology development and shows that there is the trend of urbanization.

Key words: Remote Sensing, GIS, loess hilly region, ecological monitor system