| Using the data of precipitation from 1961 to 2000 in different climatic zones of Tibet, the characteristics and variation trend of precipitation during growing period of highland barley are analyzed. The results show that the precipitation variability is relative large during jointing to booting stage, and the drought appears easily during this stage in the warm semiarid and semi-humid agricultural zone. The precipitation during heading to milk stage in the semi-humid zones meets the water requirement of highland barley in most years, and there is even surplus margin. In past 40 years, the precipitation change trend during the whole growth period of highland barley showed a remarkable decrease in the warm semiarid zone before 1980, while the increase of precipitation was significant after 1981; there was an obvious increase in the warm semi-humid zone and an insignificant decrease in the cool semi-humid zone. |