The process of a dam breach is very complex, and the resulting flood can pose a great threat to the personal and property safety of downstream residents. By using numerical analysis to simulate and analyze the sensitivity of parameters in the breach process of a large dam, it is of great significance for the formulation of emergency plans and rescue plans downstream of the dammed lake. Taking the Tangjiashan landslide dammed lake as an example, a three-dimensional numerical model of the Tangjiashan landslide dam was established based on the elevation data obtained from satellite remote sensing measurements using Autodesk Civil3D software. The Flow-3D software was used to simulate the dam breach process, and the rationality of the model was verified by comparing it with the measured breach flow rate on site.The sensitivity analysis of parameters showed that the initial breach water level had a significant impact on the breach process. Excavating the spillway channel can effectively lower the water level in the dammed lake during the breach, thereby reducing the peak flow rate of the breach and is an effective solution to control hazard losses.