In this study

the MSS images taken in 1975

1978 and 1983 were interpreted through appling geographical and optical methods

the choise of the projects of the combination of non-standard pseudo colors and the pseudo colourization of numbered phase picture produced by grating. Ac-coding to the calculation

the area of seriously desertificated pastures is about 352

000 ha.

it is 5% of the natural pastures in Hulun Beier Grassland; the area of moderately desertificated pastures is about 1

085

866.7 ha.

it is 15.4%; the area of slightly desertificated pastures is about 1

021

333.3 ha.

it is 14.4%.The windy weather and abundent sandy materials constituted the potentialities of desertification in this area

the destructive activities on vegetation during the utilizing of grassland is the main causal force of desertification.In the process of stepwise regression

statistical significance being 0.01

the strength of wind

the content of clay and organic matter in soil and the annual precipitation are not dominant. The relationship between desertificated degree and the coverage of grass is as follows T = 0.07568 + 0.00810V R=0.731where T = content of sand （0.005-0.1） in A/content of sand （0.005-0.01） in ABV = coverage of grassFrom this formula

critical coverage of grass for various degrees of desertification can be derived. The grassland may be prevented from desertification if the coverage of grass is kept above 77%

moderately and seriously desertification may occur within 52%-40% and below 40% respectively. So it is important to protect the vegetation in order to prevent grassland from desertification.