Identifying the relationships among characteristics of the source and sink landscape and runoff and sediment will help quantifying the interactions between landscape pattern and ecological processes. This study analyzed the coupled impacts from changes in the source sink landscape and precipitation patterns on runoff and sediment at the source watershed of the Weihe River, which located in the ecotone of the Loess Plateau and the western Qinling Mountain. The location-weighted landscape index (LWLI) based on the Source-sink Landscape Model (SSLM) was used to quantitatively characterize the changes of landscape pattern. The results included:(1) the area proportion of the sink landscapes increased from 1982 to 2017 and became larger than the source landscapes. The changes of source and sink landscape mainly happened in the hilly regions of the Loess Plateau. The LWLI decreased from 1982 to 2017, with substantial decrease between 1995 and 2010. (2) The major factors affecting runoff and sediment were explicitly different. The peak flow and sediment concentration substantially decreased from 1982 to 2017 and had close correlations with area proportion of "source" landscapes and the LWLI values. However, the amount of annual runoff fluctuated during the study period due to variation of precipitation and had limited correlation with changes of the landscape pattern. (3) The LWLI had close relationships with peak flow and sediment concentration by comparing the relative variable importance of landscape to climatic factors, while precipitation was the major factor affecting runoff. Moreover, characteristics of landscape pattern were regulated by latitude and migration distance and had stronger impacts on runoff and sediment concentration than slope in the study area. Results of the study suggested that changes in the pattern of "source-sink" landscape and precipitation had significant influences on river channel runoff and sediment at a long-time scale, but their importance to runoff and sediment were obviously different. The reasonable planning of "source" and "sink" landscapes could effectively control soil and water loss at the watershed scale. For land use planning and policy-making, optimization of landscape configuration should be considered to improve water and soil conservation.