Abstract: Typhoon-triggered debris flow refers to the debris flow that was triggered by typhoon storm. By regression analysis, it is found that debris flow multi-outbreak and the huge rainfall intensity were almost synchronizing, but traditional debris flow initiating theory can hardly explain this phenomenon. On the basis of analyzing the initiating process of typhoon-triggered debris flow, a two-dimension limit equilibrium analytic model was introduced to analyze the failure process of the slope in the forming area of the debris flow watershed in terms of stability, while the huge rainfall intensity in short duration come along. It is supposed that in the early stage of the typhoon influence, the slope was on the underground water seepage stage, as the water infiltrated into the slope, the matric suction in the soil reduced, and effective stress descended. The huge rainfall intensity in short duration played a pivotal role; notable overland runoff appeared on the slope surface, the sliding force of the slope was expanded by the shearing force of the overland runoff fand the slope failed more quickly. It explained the synchronizing phenomenon well. Finally, through statistical analysis, it was found that the debris flow initiating efficiency is relevant to the proportion of the tributary ditch initiating.