Abstract: This study focuses on a high-steep rock slope along the Dadu River in Luding County, systematically investigating slope instability mechanisms governed by discrete fracture networks(DFN). Given the complex geological structures and intensively developed fracture networks in the study area, we integrated field exploration data from adits to characterize engineering geological conditions. A combined approach of 3D geological modeling and simplified DFN modeling was adopted. Using the 3DEC numerical simulation program, we reconstructed the realistic structural framework of fracture-divided rock masses. The influence mechanisms on slope stability were analyzed through three key factors: fracture cutting depth, mechanical parameters of fracture surfaces, and density of fracture intersections. The results demonstrate that fracture penetration depth significantly impacts displacement field propagation. At depths of 56~66 m, maximum slope displacement reaches 20 cm, with displacement concentration zones overlapping tensile plastic zones, indicating localized landslide risks. Displacement decrease outward from fracture centers, exhibiting a characteristic Omega-shaped distribution(high in the middle, low at the ends). DFN mechanical parameters exhibit high sensitivity to slope stability. Every 0.1 increase in cohesion and internal friction angle reduction factors induces linear growth in surface displacement and exponential acceleration of plastic zone expansion, revealing a chain reaction:"local shear failure → stress concentration in adjacent blocks → cooperative damage zone progression". Fracture quantity substantially alters mechanical responses. DFN models outperform non-fractured or single-dominant-joint models in reflecting true displacement fields and plastic zones, with complex rock structures amplifying displacements by up to 200% and inducing sporadic plastic zone propagation. The research further identifies a dual-control failure mechanism: macro-scale shear slip along interfaces versus micro-scale tensile fracture-network dominance. This work provides theoretical foundations and engineering references for stability assessment and hazard prevention of high-steep fractured rock slopes.