<p>To clarify the time-dependent evolution of pile-soil interaction and the variation of negative skin friction in pile foundations at high backfill loess sites, and to reveal the impact of internal force changes on the long-term performance of pile foundations, this study considers the creep deformation of backfilled loess. The finite difference software FLAC3D is used in combination with the Burgers constitutive model to simulate the creep behavior of the backfill. The time-dependent evolution of internal forces, displacement, and the neutral point of rock-socketed piles under varying backfill heights is analyzed. The results show that the displacement of the pile lags behind the settlement of the surrounding backfill soil. Changes in backfill height lead to significant increases in both pile settlement and internal forces. After creep stabilization, there is a substantial difference in axial force distribution compared to the non-creep condition. The negative skin friction coefficient of pile foundations in high backfill loess sites is approximately 0.03 and 0.14 times of the backfill height, the factor of safety (FS) reduces from 2 to 1.79 for a single pile. Thus, the reduction in the FS significantly affects the total load capacity in the design. Thus, to ensure the long-term safety of piles at high backfill loess sites, the evolution of the negative friction that is due to creep needs to be considered.</p>