Abstract: Loess landslides occur frequently on the Loess Plateau, and their occurrence is intricately associated with seepage forces.To clarify the failure mechanism of loess slope under the combined influence of seasonal continuous rainfall and upward seepage forces from the underlying confined water, this study selects the Hongya Village landslide in Qinghai Province as a case for investigation.Based on comprehensive on-site investigations, numerical simulations were systematically carried out to characterize the response features and spatio-temporal evolution of the physical and mechanical properties of slope materials under rainfall infiltration and upward seepage conditions.Analysis of the simulated slope stability and stress-strain characteristics revealed a progressive failure process and emphasized the decisive functions of both rainfall and the confined water.The results indicate that the Neogene strata and the overlying loess-mudstone binary structure create geological conditions favorable for slope instability.A well-developed hydrogeological environment and sufficient rainfall recharge offer the necessary conditions for seepage forces to develop.Sustained rainfall is a significant triggering factor for the Hongya Village landslide, while the upward seepage of the confined water serves as the dominant controlling factor.