In order to estimate the relative impact of climate change and human activities on the change of runoff in the Zishui River Basin in Hunan Province, the cumulative anomaly curve and sliding t-test were used to analyze the trend and runoff test of precipitation and runoff series in the past 55 years. The comparative method of the slope changing ratio of cumulative quantity and the method of double mass curve were used to calculate the contribution rate of precipitation and human activities. The results show that there is an obvious impact of human activities at the Luojiamiao Station in the upper reaches of the Zishui River. In the variation period I (1987-2001), the effect of precipitation on runoff is larger than that of human activities. In the variation period II (2002-2014), the contribution rate of human activities increased significantly and gradually became the main driving factor of runoff change.