Abstract: This study adopts a bidirectionally coupled SPH numerical model to accurately simulate the full evolution of a landslide-dammed lake disaster chain. The model captures large deformation of the landslide body using the Drucker–Prager criterion and achieves water–soil coupling through mixture theory and nonlinear seepage drag forces. Validated against laboratory experiments, the model successfully reproduces the Baige landslide disaster chain, with simulation results closely matching field observations. Results show that the processes of landslide motion, impulse wave generation, and dam formation can be clearly delineated by the evolution of landslide velocity and energy. Quantitative analysis reveals that increasing the internal friction angle φ from 5° to 20° leads to a linear decrease in dam length, a power-law increase in dam height, and a significant reduction in wave height. The peak wave height exhibits a linear correlation with the landslide Froude number at impact. These findings highlight the systematic influence of landslide material properties on disaster chain dynamics and offer theoretical support for hazard prediction and risk assessment in mountainous river basins.