Abstract: The sources of the three great rivers (namely the Yangtze River,Yellow River and Lantsing River) are known as the water tower of the Chinese nation,and they are also the places where the Tibetan people have been living,who used to take a nomadic way of multiple-livestock breeding,taking pastureland by turns and pasturing shallowly,which has effectively protected the weak ecological system and made the frozen earth stable.However,with the change of property right of the pastureland and the advance of fence project,the weak ecological system was damaged,causing ecological disaster and threatening the safety of the water tower of the Chinese nation.Great attentions should be paid to this.

Key words: Tibetan people, take pastureland by turns and pasture shallowly, the sources of the three great rivers, safety of water resources