Abstract: In the upstream of the Lantsang River, there is a plan to construct the RM hydropower station. Its reservoir operation could potentially trigger deformation and instability of the RS giant deposit on the left bank near the dam, leading to landslide wave disasters and posing threats to the safety of dam infrastructure and downstream residents. This study combines extensive geological surveys and physical mechanics experiments to investigate the potential instability and failure modes of the RS deposit under reservoir filling. Based on this, a three-dimensional numerical model of the entire river channel from the RS deposit to the dam section was established. An analysis of the dynamic evolution of landslide-wave chain disasters caused by the RS deposit was conducted, predicting parameters such as the initial wave height, wave height along the opposite bank, propagation characteristics, wave height at the dam front, and height of wave climbing along the dam. The results indicate that as the reservoir water level gradually rises, the RS deposit is most likely to undergo significant instability and large-scale failure above a reservoir level of 2800m. The rear rupture boundary is identified as the gravel layer of the deposit, while the front shear boundary is the fine particle layer in the middle and lower parts of the deposit. The instability and failure of the deposit lead to the triggering of landslide waves, with the peak wave height reaching approximately 31.5m near the water inlet and lasting about 15s. As the wave propagates downstream, there is a decrease in wave height of 39.5% at the No. 1 river bay, reaching the dam in approximately 147s and continuing to climb along the dam slope. The climbing wave height is approximately 2.6m and lasts for 180s, with no risk of overtopping by the initial or subsequent smaller waves. After being impeded by the dam, the initial wave propagates upstream, creating a backflow phenomenon, which, combined with subsequent waves, forms a locally high wave area. At monitoring point P5, the maximum backflow wave height reaches approximately 4.56m and lasts for 219s. During the wave propagation process, the topography of the river bay and backflow phenomena significantly accelerate the energy dissipation of the waves, effectively reducing the risk of wave impact and secondary disaster.