Landslides have attracted widespread attention because of their tremendous ability to harm human lives and property. Many studies have focused on specific landslides to determine the relationships among the occurrence of well-known landslides and topographic, morphological and lithological conditions. Further studies need to examine the common growth rules of landslides at regional scales. For example, the Yalong River Basin is one of the regions in Southwest China where large-scale landslides are prone to occur. To determine the distribution rule of landslides for different slope azimuths, gradients and elevations in this region, the contributing weighting method (CWM) was applied. A total of 120 large-scale landslide examples were used in this study. Slope azimuths, gradients, elevations, and topographic properties were selected as event-controlling parameters, while landslide quantities, areas and volumes were selected as the reference factors. We divided those parameters into several intervals. Finally, the contributing ratios of each interval were determined and divided into high, medium, and low susceptibility contributing ratios. The assessment results were supported by the certainty factor (CF) model. In the middle and lower reaches of the Yalong River, when slope azimuths are NE and E, slope elevations are 1800–2500 m, slope gradients are 20° to 40°, and topographic conditions consist of narrow ridges, the susceptibility to large-scale landslides is high, and the slopes are more prone to large-scale landslides. The role of seismic events, regional tectonic activity and incision by water currents as a result of the assessment was also briefly discussed.