| There is a strong relationship between the vegetation cover and stability of oasis ecosystem which is the key location of mankind production and existence in arid and semi-arid land. The change of vegetation cover in arid and semi-arid has very important influence on the oasis eco-system, as it is very sensitive to the environment changes to oasis direction or to desert direction that the fluctuating index of vegetation cover. The vegetation cover rate change great effect on realizing the characteristic. So the main purpose of this research is use time series, by the means of RS (remote sensing) and GIS (Geographic Information System), on the groundwork of preciser classification data, to understand the change of different types of vegetation cover in the western arid lands in China, and to forecast future trend of the eco-environment of different areas.1. In this article, choose the FVC index for originals data which has great sensitivity to vegetation cover rate in arid lands as an environmental indicator;2. Developed a method to classify RS data based on different areas and altitudes in western arid-lands in China;3. Developed a new method: using the high resolution data to validate the data of low resolution and using this kind of method to testify the result of classified RS data in this article. The method is a useful supplement to traditional methods, especially in classification for past RS data;4. Developed classification systems of vegetation cover in arid land of western China, and use the changing of vegetation area of serial times to analyze the change of the vegetation in each area in arid land of western China.5. Using by the method of Difference Analyze and the theory of Regression Analyze, the analyzed the spatial characteristic of vegetation change in arid land6. Developed the theory and method to distinguish the stable areas from changing areas using the F' test and T' test.7. made use of Regression equation to estimate the change of vegetation, the result have some reference values.8. Successfully applied MARKOV process to analyze the change of vegetation cover, and point out the change of vegetation transition is not a single MARKOV process but a multi-MARKOV process and also is a long term process.9. The writer proved that under the 8km resolution, the MARKOV process can't estimate the trend of land use by two term-data no matter it's sequence or at intervals. Through analyzing the change of each vegetation area, the change of spatial data and the MARKOV process, the main conclusions are: In plain of China western arid land, the desert area decreased and the oasis area increased, most of the increase represents extension of the traditional oasis. The area of middle and high vegetation descended, most of the oasis directly face the desert. In the mountain area, the change of no vegetation area was not obvious, and the area of forest increased a bit. In different areas, the situations were different. In the plain area of southern Xinjiang, the areas of oasis were increased; the area of desert basically hasn't any change. The others showed partly decreased, but the degradation of vegetation were obviously in lower reaches of Tarim and Cherchen River; in the mountain area of southern Xingjian, the forest area were increased, and the others decreased; in northern Xingjian, both the mountain and the plain area increased. They showed the decrease of desert and the increase of oasis; the change of vegetation cover in the Hexi corridor-Alax desert were not obviously; but in Chai-damu basin, the area of desert and low cover grassland increased, the others vegetation decreased, especially in the high cover grassland. That showed the great degradation of ecosystem, and the most of degradation was shown in the north hillside of the Arjin Mountain and Qi-lian Mountain. These conclusions were all got corroborate mutually in every kind of analysis.The writer points out: In the western arid lands in China, desert is stability landscape, the area of the oasis is extend,...
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