Abstract: Tibet Autonomous Region is one of the main pasturing areas in China,with an area of the grass lands of 82.0519 millions hm² which accounts for 68.1% of the total territory area in Tibet and 20% of the total grass land in China. The grass lands of Tibet Autonomous Region is an important ecological protective screen for southwest region in China. Ecological environment is very fragile,and unreasonable use of grass land by human beings is strong and global climate is being changed,so,some degradation phenomena have been found such that the height of the grass community is decreased,cover rate and yield of the grasses are also decreased, dominant species of the grass communities are being changed,and harmfulness of poisonous weeds and rats has become more serious. Finally, six prevention countermeasures are suggested:change ideas,and set up guiding ideology that lays stress on both livestocks and grasses;strengthen administra tive organization construction,and manage the grass lands by the government laws;stabilize use right of the grass lands,and make it perfect for contracting resp onsibility system for grasses and livestocks;realize transform of animal husbandry of the grass lands from quantitative increasing to better quality and higher profit; adjust livestocks structure,and make reasonable distribution of the livestocks;strengthen basic and applied research in the animal husbandry.