Abstract: There are a large quantity of wide-gentle gullies and narrow-steep gullies in upstream of Minjiang River basin.The geometry of gullies has important influences on kinetic characteristics of debris flows.Taking Taoguangou gully, a wide-gentle gully in the upper reaches of Minjiang River, as the research object, we used Massflow software to simulate the dynamic process of debris flow in the gully, and the dynamic characteristics of debris flow with "narrow-steep branch channel+wide-gentle main channel, or wide-gentle branch channel+wide-gentle main channel" were obtained.The results show that the combination of wide-gentle channels of different levels in the basin has a significant effect on the initiation mode and behavior of debris flows, which affects the velocity and mud depth of debris flows.Under the combination of "narrow-steep+wide-gentle",the flow velocity of debris flow is large in the early stage, the effect of down-cutting is obvious, the run-out path is long, and the sedimentation is more in the later stage.Under the combination of "wide-gentle+wide-gentle",the lateral erosion effect of debris flow in the trench is more significant, which intensifies the evolution of the trench.Both the two combinations have the risk of blocking the river and developing into a barrier lake.This study improves the understanding of the influence of wide-gentle channel combination on debris flow migration and is helpful to the future risk assessment of debris flow.