Abstract: Abstract: The Loess Plateau is the region with the most concentrated and largest loess area in the world. It is also one of the regions suffering the most severe water and soil erosion and with the most fragile eco-environment. Loess Plateau features complex and diverse landform with ravines and gullies criss-cross. It is a key region for implementing water and soil conservation and ecological restoration in China. With this regard, researches on spatial distribution of soil erosion are quite necessary. In the common basin soil erosion models used at home and abroad, the most widely applied erosion factor is the rainfall erosivity, which reflects the comprehensive effect of raindrop splash on soil erosion, but does not reflect the effects of runoff erosion and sediment transport during water erosion process, while runoff erosion power may better reflect the comprehensive effect of water erosion force from the perspective of the energy. This research introduces the concept of runoff erosion power of storm. It extends the runoff erosion power of a single storm to a year scale based on the simulation results with SWAT (soil and water assessment tool) model in Yanhe River Basin, and obtains the annual runoff erosion power of each sub-stream. Then, researches on spatial distribution and spatial scale are performed, so as to reveal the impact of different spatial distributions and spatial scales on the water erosion process. The results show that in the SWAT model, Yanhe Basin is divided into 81 sub-streams, and the simulation effects are good, which proves that the SWAT model is feasible in this region, and can reflect the actual water regime of this basin. Runoff erosion power of Yanhe Basin has regular spatial distribution, i.e. “large in tributary, small in main stream; large at upstream, small at downstream; large in the south and small in the north”. Besides, runoff erosion power of possesses present obvious spatial scale effect. The runoff erosion power is in power function relation with the control area of sub-stream outlet section, and the threshold of spatial scale effect is at about 155 km2, and is in exponential relation with the river length above the sub-stream outlet section. The spatial scale effect thresholds of runoff erosion power of the Xingzi River, the Xichuan River and the Yanhe River are 53, 90 and 17 km, respectively. The spatial scale effect is different due to the different spatial position. In addition, the spatial scale factor, river network density and other factors will also affect the runoff erosion power. The spatial scale has a significant effect on most areas of the Yanhe River, and the main stream is mainly affected. The density of the river network has a great influence on the runoff erosion power in the tributary distribution area, but has no effect on the mainstream area. This research has clarified spatial distribution and scale effect of the water erosion power in Yanhe Basin, which provides the theoretical support for implementation of specific land and water resources management, water and soil conservation projects and ecological restoration measures in the regions along Yanhe Basin.