Climate change and land use tend to affect watershed runoff simultaneously,which could potentially have a strong effect on the quantity and quality of water resources. This paper takes Liuyang River Basin as an example,to quantitatively assessing the synergistic impacts of runoff caused by land use and climate change in the future by applying SWAT model and scenario analysis. Firstly,the CA - Markov model was utilized to simulate spatial land use patterns of the study area in the years 2020 and 2050. Secondly,the weather data from WorldClim were obtained to represent the future climate change in study area. Lastly,SWAT model was established in Liuyang River Basin to simulate the runoff and thus quantitatively evaluate the effects of land use and climate change on runoff in the future. Results showed the area of forest would decrease,but the urban constructions and cultivated land would increase in the future. The future weather in Liuyang River Basin tends to be warmer and drier. The runoff of the Langli Station in the basin was anticipated to decline to 2. 42 m~3 /s in 2020 and 0. 96 m~3 /s in 2050 under the land use change scenarios. The runoff was declined to 3. 02 m~3 /s in 2020 and 1. 13 m~3 /s in 2050 under the climate change scenarios. Under the land use and climate change scenarios,the runoff was predicted to be decreased to 8. 54 m~3 /s and 4. 27 m~3 /s in 2020 and 2050,respectively. It revealed that the runoff in Liuyang River Basin tends to be more sensitive to climate change. In addition,the synthesized impacts of land use change and climate change to Liuyang River basin is nonlinear.