Abstract: Ash-sediment—a complex mixture of wildfire ash and surface mineral soil that has lost its structure due to high-temperature combustion—is highly susceptible to erosion by runoff. Its abundance strongly influences hillslope erosion processes and the sediment supply for post-fire debris flows. This study examined burned areas with different lithologies in southwestern Sichuan, including sedimentary rocks(Xichang wildfire of March 30,2020), igneous rocks(Mianning wildfire of April 20,2020), and metamorphic rocks(Jiulong wildfire of February 16,2022). The spatial distribution of ash-sediment in each burned area was investigated, and the relationships among ash-sediment, litter, and soil erodibility were analyzed. The results indicate that ash-sediment thickness and mass load are positively correlated with fire severity. Bulk density of ash-sediment showed no significant difference between low-and moderate-severity areas but increased significantly in high-severity zones. Furthermore, due to differences in litter and soil properties, ash-sediment thickness, bulk density, and load varied notably among the burned areas, with the highest values in the Jiulong area, followed by Mianning and Xichang. Ash-sediment thickness and load were significantly positively correlated with litter thickness and soil erodibility factors. Higher soil erodibility factors corresponded to soils more prone to structural loss and loosening under high temperatures. These findings provide a scientific basis for understanding variations in sediment supply for post-fire debris flows across different lithological settings and support disaster prevention and mitigation efforts in burned areas.