<p>Reservoir landslides and landslide-induced impulse waves constitute significant global hazards for river systems and reservoir areas, with the resulting destruction often exceeding that due to the landslide itself by posing threats to shoreline residents and infrastructure and disrupting normal reservoir operations. In this study, we focused on the Wangjiaping (WJP) landslide within the Baihetan Hydropower Station reservoir in Southwest China and integrated field investigations with interferometric synthetic aperture radar (InSAR) and Global Navigation Satellite System (GNSS) monitoring to characterize the landslide's geomorphological and geological features and develop a three-dimensional numerical model for simulating landslide-induced impulse waves. The results demonstrate that the WJP landslide exhibited a distinct phased deformation response during reservoir water-level fluctuations, reflecting a dynamic adjustment process of the displacement field under the influence of reservoir water. Under reservoir water-related impacts, its failure mechanism evolves sequentially through creep deformation, tension cracking, and shear failure. Impulse wave simulations under varying water levels revealed that the initial wave height at low water levels was large but decreased rapidly, whereas waves at high water levels were smaller but could propagate over longer distances and broader areas. At a water level of 825&#xa0;m, the maximum wave height upon reaching the opposite bank and downstream settlements following a global failure of the landslide was less than 1.6&#xa0;m, representing a generally low threat; however, short-term high-amplitude fluctuations may occur in nearshore areas, and the risk cannot be ignored if compounded by extreme hydrometeorological conditions. This study provides a scientific basis for the early identification, risk management, and formulation of differentiated prevention and control strategies for reservoir landslide-induced impulse wave hazards.</p>