As the only water drinking resource in Beijing, the Miyun Reservoir is still suffered over ten thousand tons of sediment input from its upper catchment. Explicating sediment sources of the catchment upstream of the reservoir is urgently required to further implement soil conservation measures. In this paper, the Revised Universal Soil Loss Equation (RUSLE) and Sediment Delivery (SEDD) models were combined to explicate the major sediment source of the catchment through exploring the spatial distributions of soil erosion and sediment delivery as well as their relations with land use and topography, and sediment source areas were then identified. The catchment average soil erosion intensity (SEI) of 4.08 t ha− 1 yr− 1 was two times the soil loss tolerance (T = 2.00 t ha− 1 yr− 1) of the study region. The values of cell sediment delivery ratio (SDR) showed a network distribution pattern, ranging from zero to unit, with an average of 1.65%. Cell specific sediment yield (SSY) presented a similar spatial pattern to SDR, ranging from 0 to 902 t ha− 1 yr− 1, with an average of 0.04 t ha− 1 yr− 1. Bare land suffered the highest SEI of 39.01 t ha− 1 yr− 1, followed by shrub land and orchard field. Nearly 70% of the sediment came from grass land. Farmland was the second sediment contributor. Grass land and farmland are the two major sediment source areas. Soil conservation practices should be further implemented on these lands, especially on the 3–5°slopes with elevations less than 500 m a.s.l.