In this study,the hydrological model of distributed MIKE SHE was used to calibrate and validate the change of monthly and annual runoff volumes at the hydrometric stations in the mainstream area of the Tarim River. The study was based on the air temperature and precipitation data observed by the meteorological stations named as Aral,Baicheng,Kuqa,Luntai,Korla and Tikanlik during the period of 1998 - 2007,and also the discharge data measured by three hydrometric stations including Xinquman,Yengbazar,and Qara during the period of 1998 - 2007. The climate model of HadGEM 2-ES was used to estimate the evolvement of runoff volume of mainstream of the Tarim River in the future ( from 2021 to 2050) under climate scenarios. The results indicated that: ① The model of MIKE SHE was adopted to simulate the runoff process of mainstream of the Tarim River,and the model efficiency coefficients were all higher than 0.63,which showed that the applicability of this model was high; ② In the next 30 years,the monthly average temperature in the mainstream area of the Tarim River would be increased by 1.7 - 2.2 ℃ compared with that during the reference period ( from 1981 to 2004) ,and the temperature increase in summer and autumn would be significant. Precipitation would be in an increase trend,its increase would be significant in spring but not in autumn; ③ Under the future climate scenarios,annual runoff volumes at the hydrometric stations would be in a decrease trend,especially in summer and autumn ( P < 0.01) . In which the decrease of runoff volume at Qara Hydrometric Station in the lower reaches would be the most significantly ( 5.04%) , but that at Xinquman Hydrometric Station in the upper reaches was the lowest ( 0.6%) . In emission scenarios under various climatic conditions,the reduction of runoff volume was the least under RCP 2.6 ( low emission) but the most under RCP 8.5 ( high emission) . The annual runoff volume of mainstream of the Tarim River under the future climate scenarios would be in a decrease trend,it would be more difficult to redistribute water resources,the ecological security would be threatened,and the human-land contradiction would become more serious.