Abstract: Understanding the interaction mechanisms between slope excavation and adjacent underground structures is critical for ensuring construction safety in complex geological environments. This study established a three-dimensional numerical model of a slope-underground grain-silo system using FLAC^3D software to investigate the coupled response during staged excavation. Five sequential unloading steps were simulated to capture progressive stability evolution and structural disturbance patterns. A characteristic parameter framework comprising six indicators was developed to quantitatively characterize soil-structure interaction. The results show that slope stability progressively degraded,with the stability factor decreasing from 1.36 to 1.02,exhibiting a depth-dependent response characterized by pronounced deep-zone deformation and upward attenuation. The grain silo demonstrated spatially heterogeneous responses: the roof emerged as the critical zone,with maximum strain increments reaching 20‰ and experiencing a stress-path transition from triaxial confinement to a"lateral unloading-vertical loading" state,while the main body maintained structural integrity. Stress-path analysis revealed that the slope-silo interaction was governed by load-transfer mechanisms,forming a"slope unloading-silo bearing" pattern. The proposed characteristic parameter system successfully captured system evolution,with key parameters identifying critical turning points during excavation stages. These findings elucidate the interaction mechanisms in slope-structure systems and provide practical tools for stability assessment and protective design in similar geotechnical projects.