Abstract: Linear regression and Mann-Kendall non-parametric test were first used to analyze the change characteristics of the hydrological and meteorological elements in the water source area (catchment) of the Middle Route Project of South-to-North Water Transfer; then a distributed hydrological SWAT model was developed based on a digital elevation model and the land use and soil type information, and its applicability in the catchment was also verified. Finally, the precipitation, temperature and runoff response processes were analyzed based on the IPCC Fourth Assessment Report multi-mode ensembles under different greenhouse gas emission scenarios (SRES A2 and A1B) in 2011-2050. The analysis results show that precipitation in the catchment had no trend, temperature rose slowly, and surface runoff decreased slowly during 1961-2000. Compared with the baseline period, precipitation, temperature and runoff in the catchment in future 40 years will all increase under the A2 and A1B scenarios, especially under the A2 scenario, but the increment amplitude of runoff will be less than that of precipitation, this may be associated with the increase in evaporation. Future climate change will have a little influence on the runoff of the water source area, and thus will generally be favorable to the South to North Water Transfer Project.