Given that the Nizeng landslide is located within the reservoir area of the Batang hydropower station and the landslide shear outlet is below the normal water level of the reservoir, the reservoir's water storage will inevitably affect the stability of the landslide, affecting the lives and property of nearly a hundred households on the slope. This article takes the Nizeng landslide in the reservoir area of Batang Hydropower Station as the research object. Through a systematic investigation of the engineering geological conditions of the landslide area, comprehensive analysis is conducted from multiple dimensions such as morphological characteristics, scale parameters, boundary conditions, material composition, and deformation and failure characteristics. The formation conditions and evolution mechanism of the landslide are deeply studied. Based on numerical simulation methods, the stability evolution law of landslides under different working conditions before and after reservoir water storage was quantitatively evaluated. The research results indicate that under normal working conditions, the Nizeng landslide maintains a stable state before and after water storage; However, when the reservoir encounters extreme conditions such as rainstorm or earthquake after impoundment, there is a risk of local instability at the shallow surface of the front edge of the landslide. This research result can provide scientific basis for landslide disaster prevention and control in the reservoir area.