Abstract: In recent years, the significant increase in land resource demands in loess gully regions has led to rapid development of fill engineering projects, accompanied by increasingly prominent landslide hazards. While altering the original topography, these projects substantially modify the stress state of soil mass, with moisture content and confining pressure fluctuations becoming critical factors affecting slope stability. This study focuses on a loess-filled slope in Tianshui City, conducting a series of triaxial creep tests under controlled moisture content and confining pressure. The results demonstrate: (1) Increased moisture content weakens soil structure and reduces soil strength, while higher confining pressure restricts lateral deformation. (2) During moisture content elevation, the failure mode transitions from brittle fracture to plastic bulging (notably at 24% moisture content), with significantly increased axial compression. (3) Moisture content increase elevates pore water pressure, shifting the Mohr circle leftward; meanwhile, long-term creep effects reduce shear strength through decreased effective stress and moisture-induced cementation weakening, triggering shear failure when the Mohr circle boundary exceeds the new strength threshold. (4) Although confining pressure enhances long-term soil strength, stress redistribution in actual projects causes shear stress concentration at the slope toe as fill height increases, ultimately reducing slope stability. This study systematically reveals the creep behavior, failure characteristics, and stress evolution of filled slopes under varying moisture content and confining pressure conditions, providing experimental references and theoretical foundations for stability control in loess-filled engineering projects.