Abstract: Based on the interpretation of the Landsat-TM data which was with 82 digital images taken in 1990 and 2000 respectively,the landscape structure and its changes of the grassland in the Northern Tibet were studied to reveal the land use change by analyzing the indices of patch-size,spatial pattern and other parameters commonly used in landscape ecology.The preliminary results were as follows: 1) Alpine grasslands were the main landscape types in the Northern Tibet.2) From 1990 to 2000,the alpine desert expanded greatly,while the areas of the landscape types,such as alpine meadow,the alpine grassland,glaciers and snow mountains decreased,which deteriorated the regional eco-environment.The expanding of the water area lessoned the deterioration of eco-environment to a certain extent,but also brought the flooding disaster in some regions and reduced the grassland area.3) The landscape pattern there had an obvious trend of fragmentation due to the ever-increasing human activities.

Key words: Landsat-TM data, Landsat-TM data, Northern Tibet, Landscape structure, Land use change