This paper conducts a systematic study on the stress and deformation of ultra-long pile foundations in slope accumulations under sliding loads. Existing research lacks sufficient analysis of the bearing capacity and stability of pile groups under complex load conditions, increasing the risk of overall collapse of engineering structures under landslide effects. To address this, a numerical model of pile foundations in typical slope accumulations was established using finite element analysis software, based on practical engineering applications. The deformation, pile-soil interaction, and overall stability of the pile group foundation were studied under different landslide intensities. The paper focuses on analyzing the load-bearing behavior of rear piles, the impact mechanism of superstructure loads on pile foundations, and the effectiveness of anti-slide pile reinforcement. The study found that rear piles are most adversely affected by loads under landslide conditions, with the maximum internal force occurring near the pile top or sliding surface. The improvement of pile foundation bending moments and horizontal displacement due to superstructure loads is limited, but their impact on shear forces is significant. Additionally, rear anti-slide pile reinforcement is most effective, with the optimal reinforcement distance being 2-4 times the cross-sectional length of the anti-slide pile. The research results provide a theoretical basis for the design and construction of ultra-long pile foundations in slope accumulations and offer reference for the response analysis and optimization design of ultra-long pile foundations under sliding loads.