The hydrological processes are largely influenced by climate variability and human activities, and the quantitative assessment of their impacts on runoff change is a hot issue in hydrological scientific research. With the quantitative assessment method of runoff change based on SWAT model, this study uses long hydro- climatic data of the Luanhe River Catchment to quantitatively assess the runoffs response to climate variability and human activities. By using Mann- Kendall method, the whole runoff time series were divided into three periods: baseline period, variability period I and II. Then the contribution rates of climate variability and human activities on runoff change in variability period I and II were analyzed with quantitative assessment method. The results show that there was a statistically significant decreasing trend of annual runoff during 1960- 2010. Compared with the average annual runoff in baseline period,the average annual runoff in variability period I and II decreased 49.71% and 70.03%, respectively. So the impact of climate variability and human activities on the runoff became much stronger. And the human activities were the main factors for the runoff decrease. In variability period I, the contribution rates of human activities and climate change on runoffs decrease were - 26.30% and - 73.70%, respectively. While in variability period II the contribute rates of human activities and climate change on runoff decrease were -26.15% and -73.85%, respectively. As for the impact of land use change on the runoff, it reduced the runoff with the contribution rate of - 19.65% in variability period I, while it increased the runoff with the contribution rate of 3.83% in variability period II.