Abstract: Based on the interface theory, taking the corresponding surface of the yielding depth of debris flows as the interface, the viscous debris flow can be divided into ideal fluid and Bingham fluid. Thus, a numerical model and the relative algorithm are developed to simulate the evolution of debris flows. The model is based on the motion feature of the debris and cosiders the velocity differences of debris flows in different layers, thereby, it can reasonably describe the evolution mechanism and the influences on the morphology of debris flows due to the flow velocity. Meanwhile, the model fully considers the phenomena of “tongue-like” and “debris flow head” of actual debris flows, thus, the motion state of the debris flows during the evolution can be depicted accurately. A series of model tests are adopted to verify the proposed numerical model and the algorithm. The comparison between the measured and calculated results indicates that the relative errors of the inundation areas and the maximum accumulation thicknesses are within ±5%, and the rationality of the proposed model is validated.