Abstract: Statistical downscaled and bias corrected climatic outputs of four global climate models (GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC5) under historical simulation experiment (1861-2005) and RCP4.5 scenario (2006-2018) are used to drive the SWAT hydrological model to analyze the climate change and its impacts on river runoff in the Wujiang River Basin (WJRB). Meanwhile, pre-industrial control experiment (piControl) for 1861-2018 from four GCMs is also used to compare the differences of climate and streamflow changes in the WJRB under the ‘natural’ forcing and the ‘anthropogenic+natural’ forcing. Following results are reached: (1) according to the multi-model ensemble mean, annual mean temperature in the WJRB for 1861-2018 has shown an significant upward trend with a rate of 0.03℃/10a, and annual precipitation has shown a significant downward trend with rate of -10.9mm/10a. The annual average discharge has shown a significant downward trend with a rate of -20.8 m ³/s/10a. Seasonal average discharge has shown declining trend with rates of -10.8 m ³/s/10a, -46.1 m3/s/10a, -20.1 m3/s/10a, and -5.9 m ³/s/10a, respectively, for spring, summer, autumn and winter. Trends of all seasonal average discharge were statistically significant. Significant decreasing trend was detected with rate of -7.6 m ³/s/10a and -43.5 m ³/s/10a, respectively, for low flow (Q90) and high flow (Q10). (2) Under the ‘nature’ forcing, no obvious trend was detected for annual mean temperature in WJRB for 1861-2018, and an insignificant upward trend was found for annual precipitation with rate of 1.9 mm/10a. The annual average discharge was in a slight positive trend with rate of 0.1 m3/s/10a. Insignificant decrease trend was detected with rate of about -1.1 m ³/s/10a for spring average discharge, while significant one was detected with rate of about -18.6 m ³/s/10a for summer average discharge. Autumn and winter average discharge has shown increasing trend with rate of 11.0 m ³/s/10a and 8.9 m3/s/10a. The trend of autumn average discharge was statistically unsignificant, while winter average discharge was statistically significant Change of extreme discharge was insignificant, and rate of change was 2.5 m ³/s/10a and -9.5 m ³/s/10a, respectively, for low flow and high flow. (3) With relative to the ‘natural’ forcing, seasonal average discharge decreased 7.1%、9.7%、8.7%、11.9% , respectively, for spring, summer, autumn and winter, and decreased 9.3% and 5.0%, respectively, for low flow and high flow for 1861-2018.