This study analyzed the variation and abruption of runoff in the middle and lower reaches of the Weihe River, which can provide a reference for the reasonable development and utilization of water resources and promote the sustainable economic and social development. Taking four hydrological stations including Linjiacun, Xianyang, Lintong, Huaxian in the middle and lower reaches of Weihe River as an example, a moving average method, accumulative anomaly and the linear trend analysis were used to investigate the variation in the annual runoff, and the sliding t-test, a sequential clustering method and Mann Kendall method were applied to study the abruption of the annual runoff. The analysis results show that the annual runoff of the Weihe River basin has decreased since the seventies of the last century, and different hydrological stations have similar changing patterns of the annual runoff. The abruption of runoff of all hydrological stations were detected in the early 70's and early 90's of the last century. Different hydrologic stations had different abrupt points of the runoff. The abrupt points of the runoff for Linjiacun hydrological station happened in 1970 and 1990, those for Xianyang hydrological station in 1970 and during 19901992, for Lintong hydrological station in 1968 and during 19901994, and for Huaxian hydrological station in1968 and 1990. The research results reveal that the variation in annual runoff in the Weihe River was caused by both climate change and human activities. The impacts given by the climate change mainly resulted in variations of precipitation and potential evaporation in the Weihe River basin, and the impacts of human activities mainly resulted in the construction and completion of the water projects.