The Dashui gully is a right-bank branch of the Baoxing River, located in Baoxing County, one of the are- as most affected by the Lushan"4 • 20" Earthquake, Sichuan, China. The gully has a basin area of 1.01 km2, is 1.85 km long, and the gully' s longitudinal slope is 640 %. The gully was lack of sediment supply conditions be- fore the earthquake. After earthquake, 6 landslides varying in size were induced by the earthquake and distributed in the middle and lower reaches. Together with the steep high landform conditions and favorable rainfall conditions, debris flow will be easy to form and cause great damages to buildings and human lives at the outlet area. Based the satellite images interpretation before and after the earthquake and the filed investigation, the loose solid materials, catchment integrated coefficient, relative cutting degree, mean channel gradient, mean hillside gradient and stra- tum lithology were selected as identification factors. Then, the Dashui Gully was identified as an earthquake-in- duced potential debris flow torrent. The 6 landslide induced by the earthquake cover an area of 20 375 m2 with a to- tal volume of 15.20 x l04 m3. Based on the formation conditions and potential tendency, the debris flow mitigation measure was proposed and the optimal cross-section design for the trapezoid shaped debris flow drainage canal of the gully is discussed. After calculation, the width and depth of the optimal trapezoid shaped debris flow drainage canal were equal to 2.38 m and 2.23 m respectively for draining the debris flow of 50 years return period.