The Huangshui River is located in a semiarid area of northwestern China and plays a significant role in maintaining water balance and ecological health of NCP. Since the beginning of the 21st century,frequent extreme weather events have resulted in significant changes under a background of global climate change. In the past few decades,decreasing runoff in the Huangshui River Basin associated with climate variability and human activities has caused a series of water and eco-environmental problems. These have had a profound and lasting impact on the hydrologic progress. Assessing and separating the responses of runoff to these two driving factors is urgent. Based on meteorological and hydrological data from 1966-2010 and using accumulative anomaly, nonparametric Mann-Kendall test,and the change rate of accumulation slope,we analyzed runoff and climate in this region and calculated the contribution rates of climate change and human activity. The results show that annual precipitation,evaporation and runoff are decreasing. Annual runoff decreased by 0.1 hundred million m3/10a,there are periods of 4a,9a,20a and an abrupt change was identified around 1987. Climate variation accounted for 35.46% of the decrease in runoff,while human activities altered the cycle route of water in the basin,accounting for 64.54%. Human activities are a dominant influence in the decline in runoff across the Huagshui River Basin.