[Objective] The impacts of precipitation and human activities on runoff in Yuanshui River Basin and its cause were studied in order to provide scientific basis for the water utilization of Yuanshui River basin.[Methods] By using cumulative anomaly method and sliding t test, the trend and mutation test of precipitation and runoff series in recent 55 years in Yuanshui basin were carried out. The contribution rate of precipitation and human activities to runoff change in Yuanshui River basin was calculated by double cumulative curve method.[Results] In addition to Anjiang Station, which was obviously influenced by human activities, its contribution was 60%. In the period of variation Ⅰ(1989-2003), precipitation had greater impact on runoff than the contribution rate of human activities. In the period of variation Ⅱ(2004-2014), the contribution rate of human activities increased significantly and gradually became the main driving factor of runoff change.[Conclusion] In recent 55 years, the influence of human activities on runoff in the Yuanshui River basin had been increasing. The contribution rate of human activities in the lower reaches of the Yuan River basin had increased the most.