Abstract: The Haihe River Basin is the primary water supply basin in the North China Plain. The runoff generation is mainly concentrated in the soil and rocky mountains upstream. Over the past 50 years, the region has experienced a continuous decrease in runoff, resulting in water resource crisis. This paper analyses the trend of runoff over time series in 57 sub-basins with long-term hydrological and meteorological data in the mountainous areas of the Haihe River Basin. The M-K test was employed to analyse the data, and sensitivity analysis was conducted to distinguish the contributions of climate change and human activities to runoff from watersheds of different scales in the region. The study revealed that runoff from larger watersheds is more susceptible to changes in rainfall and potential evapotranspiration. It has been demonstrated that the impact of human activities is significantly greater than climate change on changes in runoff in both small- and large-scale watersheds. This effect is particularly pronounced in drier regions.