In this study,based on DELWARE temperature and precipitation data,GLDAS evapotranspiration data,and measured streamflow from nine hydrological stations located along the mainstream of the Mekong River,the regression analysis,T test and low-pass filter were used to analyze the climate and streamflow changes in the basin during the periods of 1950-2017.The results show that the average temperature of the basin is increasing,and since 2008,the temperature has increased significantly,while the average precipitation in the basin has changed little.The average evapotranspiration in the basin shows a decreasing trend in December-January,and an increasing trend in other months.The average evapotranspiration in 2008-2017 has increased significantly compared with the average evapotranspiration in 1950-2007(June-October).The annual streamflow in the basin has not changed significantly,but since 2008 the streamflow shows an increasing trend in December-April,along with a decreasing trend in July-October.The increasing trend is more obvious than the decreasing trend,and the increasing trend in January-April is more significant after 2008.For the yearly minimum streamflow,there is a significant increasing trend after 2008,and the maximum streamflow shows a decreasing trend after 2008.The streamflow reversals have increased significantly since 1990.By comparing temperature,precipitation,evapotranspiration and streamflow changes in different time periods,it can be seen that the change of streamflow after 2008 is not significantly related to the changes of natural climate,but may be significantly related to the dams' water storage capacities (human activities).