The ability to forecast debris flows is important because of their frequent occurrence and potential for large-scale damage in the Wenchuan Earthquake-hit area. Accurate understanding of the characteristics of rainfall responsible for triggering debris flows is necessary for an effective early warning procedure. This study examined the general characteristics and spatiotemporal variation of rainfall events that responsible for debris flows. Analysis was performed on rainfall data extracted during 2008-2013. The results revealed that the rainfall thresholds for debris flows varied annually and showed tendency toward higher conditions required. The coefficient of variation of relevant rainfall events indicated that the characteristics of the rainstorms changed. In addition, the coefficient of deviation revealed the spatial variation of rainfall in subregions, which was attributed to differences of the local climatic conditions that control debris flow occurrence. The primary controlling rainfall indices for triggering debris flows were filtered, and the most suitable models for establishing rainfall thresholds were selected. Ultimately, the rainfall thresholds were obtained for each subregion within the study area.