Abstract: Reasonable prediction of barrier dam breaching process is of significant importance for disaster consequences evaluation and disaster prevention and reduction work implementation. However, due to the complexity of barrier dam’s structure and materials, the prediction is full of challenges. Based on the geological survey data and breach mechanism of barrier dam, a numerical model for the overtopping-induced breaching process of barrier dam is developed, which considering the variations of barrier deposits erosion characteristics along the depth. The model mainly includes hydrodynamic module, soil erosion module and breach development module, and the numerical calculation method based on time step iteration is adopted to simulate the soil and water coupling process during dam breaching. The “11.03” Baige barrier breach was selected to verify the model with measured data, and the simulation results verified the rationality of the model. The parameter sensitivity analysis results show that the barrier soil erosion coefficient has important influence on the breaching process, the critical shear stress of barrier soil has relatively small influence on the breaching process. Further, the excavation of spillway can greatly reduce the peak breach flow for large barrier lake, which is an effective means of disaster reduction.