The ecosystem of semi-arid region

the neighboring zone of agriculture and grazing area in Inner Mongolia is very sensitive and fragile. It is urgently demanded to assess the status of regional ecological environment quality degradation and o find out potential environmental degradation area.In this paper the vegetation

soil brightness

moisture and heat indices are extracted and evaluated from multi-band and multi-time TM and MSS remote sensing data to describe ecosystem status. An ecological environment quality evaluation model is built from these indices

climate data （air temperature

precipitation

evaporation and relative moisture） and other geographical auxiliary information （geomorphologic types

terrain elevation and land use information

etc.）

on the support of GIS. The ecological environment change during 2 decades （from 1976

1987 to 1996）of middle and western Inner-Mongolia region is evaluated using this model. The ecological environment quality degradation of this region is analyzed from the aspects of average regional ecological environment quality index change

the area change of each ecological environment quality index

and from sample band analysis. Finally

this paper also analyzes the change of climate factors and the effect of these changes on ecological environment quality change quantitatively.Through correlation analysis of ecological environment quality change and climate factor change

this paper concludes that the climate changes are the major reason that leads to ecological environment degradation. By calculation of the correlation between ecological environment quality change and change of precipitation

evaporation and moisture

which is the combination of the former two factors

this paper puts forward that the major climate factor that affects ecological environment changes in semi-arid region is moisture. During the 20 years

the effect of human behavior increases a lot. Meanwhile this research also proves that the methodology used in this paper is effective.