[Objective]Studying the impacts of climate variation and land use change on annual runoff in mesoscale watershed in order to provide theoretical basis for basin water resources management and land-use planning in this region.[Method]Jiehe watershed of Loess Plateau was selected as a research area.Mann-Kendall test,accumulative anomaly curve,double mass curve and separation evaluation method were applied to quantify the respective contribution of climate and land use change to annual runoff of the area in the past 50years.[Results]The annual precipitation among the observed years were not significantly different(p> 0.05),whereas the annual runoff had a significant decreasing trend with a change point occurred in 1979(p< 0.001).Slope farmland declined sharply,terrace area increased rapidly during the study period.[Conclusions] Land-use change was the strongest contributor to the reduction in mean annual runoff of Jiehe with 90.2% contribution,and the remaining variation could be interpreted by climate change.