In order to efficiently and accurately analyze and predict the flood discharge of the dam breach of a barrier lake, the basic principles of the DL Breach model were reviewed, and the flood discharge process of the dam breach of Tangjiashan Barrier Lake was inversely analyzed and compared with the measured discharge process. The results show that the DL Breach model is reliable and stable. The discharge process of the dam breach of Tangjiashan Barrier Lake calculated by this model is close to the measured value. The calculated peak discharge is 7 323 m³/s, which is approximately 11.2% higher than the measured value of 6 500 m³/s. The calculated peak discharge occurrence time is nearly 1.h earlier than the measured time, mainly due to the fact that the small stone beam at the breach of Tangjiashan Barrier Lake enhances the anti-scouring ability of the barrier body. In addition, an increase in material particle size will reduce the erosion of the breach and decrease the peak discharge, while an increase in material cohesion, upstream slope ratio and initial breach depth will reduce the bottom elevation of the breach, but has little effect on the peak discharge.