Abstract: The discharge data of the source area of the Yangtze River are analyzed through the Mann-Kendall test.The results reveal that the annual discharge has a weak decreasing trend during 1956-2000,but has a significant decreasing trend from 1980-2000.The annual air temperature has a significant increasing trend within the basin,while the precipitation has a decreasing trend.The consistent change of discharge and precipitation,and no obvious variation of the relation between precipitation and runoff within the basin,suggest the discharge decease during the 1980-2000 period is mainly caused by the reduction of precipitation,and the increase of ice melt,and does did not offset the reduction by reason of the regional warming.The spring discharge has an increasing trend from 1956-2000,which may be attribute to the early startup period and strengthening of snow or ice melting.