Based on observation data of six representative meteorological stations in Tibet during 19712010,and using linear trend estimation,this study analyzed characteristics of climate change in the past 40 years in Tibet.We studied the changing trends of light-temperature productivity (LTPP) and climatic potential productivity (CPP) of barley and wheat in the past 40 years from six major agriculture areas in combination with the data of actual productivity.The results showed that: (1) In the past 40 years, the temperature and precipitation increased, the mean temperature increased by 2.26℃ in the six major agriculture areas,the increasing rate of mean temperature was higher than that of China (1.1℃· 100a~(-1)); (2) The LTPP of barley and wheat increased at an annual rate of 53 kg·hm~(-2) and 107 kg·hm~(-2) with the increased temperature,respectively.The CPP increased at an annual rate of 94 kg·hm~(-2) and 110 kg·hm~(-2) with a slight increasing of precipitation,respectively; (3) The changing trend of yield potential in terms of LTPP and CPP of barley and wheat decreased.For barley,there existed gap between the actual yield LTPP (10 385 kg·hm~(-2)) and CPP (5 969 kg· hm~(-2)) of barley,while those for wheat were 9 040 kg·hm~(-2) and 5 197 kg·hm~(-2),respectively.