Runoff is not only impacted by the climate change but also impacted by the human activities. The Luanhe River Basin in Inner Mongolia is located in the arid and semiarid areas of China, where there is serious water and soil loss and the environment is badly damaged. According to the analysis, the runoff is in descend trend in resent 50 years. In this paper, the SWAT hydrological model was employed to analyze the impact of climate change and human activities on runoff. The result shows that the impact of human activities is larger than climate change, and the indirect human activities are the main reasons for runoff reduction.