<p>Reservoir landslides represent a significant geological hazard, particularly in the mountainous regions of Southwest China. In hydropower reservoirs, water level fluctuations frequently trigger slope failures, threatening critical infrastructure and human safety. For rock slopes, failure typically occurs along weak interlayers, which play a decisive role in controlling slope stability during reservoir operation. This study investigates a typical bedding rock slope in the Maoergai reservoir, adopting it as the prototype for physical modeling. A three-layered slope model was constructed to simulate a rock slope containing a weak interlayer. Through a series of laboratory experiments, the dynamic response and stability of the bedding rock slope under water level fluctuations were systematically examined. The results demonstrate that the softening of the weak interlayer is the dominant factor governing slope failure. Pore water pressure evolution and water infiltration were identified as the primary mechanisms driving the progressive reduction in shear strength of the weak interlayer. Furthermore, long-term monitoring data from an actual slope in the Maoergai reservoir were analyzed and compared with experimental findings, providing field validation for the proposed failure mechanism.</p>