Abstract: Influenced by climate change and human activities, runoff in the source region of Weihe River has been decreasing. Based on the hydrological data of Wushan Hydrological Station in the source area of Weihe River and the meteorological data of three meteorological stations around it from 1975 to 2018, this study used Mann-Kendall trend test method, double-mass curve method, and Budyko hypothesis elastic coefficient method to analyze the runoff change trend and mutation characteristics in the basin, to reveal the driving factors causing runoff change, and to quantitatively analyze the influence degree of driving factors. The results showed that the annual average runoff in the source area of Weihe River from 1975 to 2018 was 4.89 × 10⁸ m³, showing a significant decreasing trend. The precipitation was 467.43 mm, and the decreasing trend was not significant. Potential evapotranspiration was 811.39 mm, showing a significant increasing trend. The year of runoff mutation in the source region of Weihe River occurred in 1993. Through the analysis of runoff sensitivity in the source area of Weihe River, it has been found that runoff showed the most sensitive to rainfall, followed by human activities and potential evapotranspiration, and the sensitivity to the three showed a significant increasing trend. Through Budyko hypothesis elastic coefficient method, it has been found that the influence of human activities on runoff change was the main factor, accounting for 54.09% of the runoff change. This was due to the large-scale implementation of returning farmland to forest and other soil and water conservation measures in the source area of the Weihe River. The formation of surface runoff has been significantly reduced.