In order to analyze the influence of land use and land cover changes on runoff regimes, a distributed hydrological model in the Jinghe Basin was built based on the SWAT model. The synthetic influence of climate change and human activities on the hydrological processes in the study area was also investigated. The results show that, before 1996, land use and land cover changes were the main human activities affecting hydrological processes; under those influences, inter-annual fluctuations of runoff were stable, showing a significant positive skew. At the intra-annual scale, the main influence was runoff in dry seasons, and the flow was more uniformly distributed than before. Meanwhile, the concentration ratio of runoff decreased, and the concentration period lagged and tended to be stable. The analysis of the physical causes of the runoff change indicates that land use and land cover changes lead to decreasing evapotranspiration, a decreasing amount of rainfall intercepted by the canopy and litter layer, and increasing infiltration in the basin, all of which cause the increase of the baseflow and surface runoff in the channel, leading to new variations of hydrological processes. The results also show that the runoff increased after 1996 due to climate change, and the main human activities changed from single land use and land cover type to land use and land cover coupled with other water-related activities. Also water-related activities, rather than climate change and land use and land cover changes, became the principal factor in the variation of hydrological processes.