Debris flow is one of the most common geological disasters in China, which would occur more actively after 5.12 Wenchuan Earthquake. Debris flow drainage canal is one of the disaster countermeasures used in the debris flow fans which acts a significant role in the mitigation and prevention hazards of debris flow. During the operation of practical projects, the useful life of the drainage canal was greatly shortened for strong abrasion on the drainage structure of debris flow. Basing on the field investigation results, the damage types of drainage canal are summarized, such as (a) Erosion of clear water flow and hyper-concentrated silt flow; (b) Impact fracture and foundation scour on the threshold of drainage canal; (c) destruction of the drainage canal outlet; (d) Debris flow ablation destruction on the drainage canal. According to the issues of destruction of the drainage canal in debris flow drainage process, a number of new type drainage canals can be proposed, including drainage canal with interlaced sill, drainage canal with symmetrical sill, and drainage canal with energy dissipation basin. Although some kind of drainage canal has applied successfully in practical disaster prevention and mitigation engineering, the motion characteristics of debris flow and the effect of energy dissipation basin is still lack of theoretical research. Therefore, the mechnism and the optimum design of the drainage canal needs further study. The systemic research results can provide reference for optimizing the design of drainage canal and it has the great significance to improve the techniques level and enlarge the application range of mitigation engineering.