Abstract: Coseismic geologic hazards of the Ms 8.0 Wenchuan Earthquake included a great amount of landslides, rockfalls and avalanches, but few debris flows. However, numerous mass movements such as landslides and avalanches are becoming a plentiful mass source for the formation of debris flows, and many debris-flow events have occurred widely since the earthquake, especially in the meizoseismal area. In this paper, debris-flow ravines at Subaohe and Weijiagou rivers in Beichuan’s Meizoseismal area, southwestern China are studied by field investigation, remote sensing image interpretation and historical data analysis. It is summarized that the formation of these debris flows in the study area can be mainly divided into three classes, viz. direct mobilization from landslide, erosion of unstable slope, and outburst of blocked flood. Other disasters such as flood, landslide, and avalanche were accompanied with the debris flows. The distribution of grains in the debris deposits concentrates on sand, cobble and boulder. The events were closely synchronous because they were triggered by the rainstorms on September, 23~24, and the locations of the ravines show some kind of space symmetry. Another notable feature is that the magnitude of debris flows is large even for those ravines with small catchment area. Finally, four countermeasures mitigating debris flows are proposed against the debris-flow hazards, which can be practically applied to debris-flow prevention.