<p>Large creeping landslides in reservoir areas experience long-term progressive deformation, often leading to sudden overall instability and posing severe threats such as landslide-dammed lake disaster chains. Accurately evaluating their dynamic stability is crucial yet challenging due to the complex stress field evolution. This study focuses on creeping landslides in reservoir areas and proposes an improved dynamic stability evaluation model that incorporates both vertical settlement and slope angle changes—two critical indicators of progressive deformation. By coupling the mechanical effects of rear-slope settlement-induced thrust and inclination-induced stress redistribution, the model better reflects the internal stress variations during the creeping process. Applied to the Menggu landslide in the Baihetan Reservoir area, the model’s calculated stability factors more accurately represent the observed evolutionary pattern of “basically stable → unstable → basically stable” than traditional approaches. An analysis of the proportional contribution to the reduction in the landslide stability factor reveals that settlement-induced deformation accounts for an average of 86.83%, while changes in slope angle contribute an average of 13.17%, highlighting the critical importance of both factors in practical stability assessments. The proposed model offers a reliable mechanical framework for real-time monitoring, early warning, and risk assessment of large creeping landslides, providing valuable guidance for geological disaster prevention.</p>