Abstract: To gain a comprehensive understanding of the longitudinal hydraulic fracture propagation mechanism in ultra-deep shale reservoirs, the study systematically analyzes the influence of high stress and bedding properties on shale fracture characteristics. Initially, shale mechanical parameters are obtained through triaxial compression experiments. Subsequently, a three-point bending numerical model of a semi-circular shale plate with confining pressure is constructed using the particle discrete element method to simulate the fracture process under various conditions. The numerical simulation results demonstrate that increasing confining pressure significantly enhances shale fracture toughness, and the influence of bedding plane angle and density on fracture toughness is amplified with increasing confining pressure. Specifically, at the same confining pressure, fracture toughness decreases with an increase in bedding plane angle and exhibits a minor variation with an increase in bedding plane density, indicating that bedding plane density has a greater strengthening effect on fracture toughness than bedding plane angle. Based on these findings, a quantitative chart illustrating the impact of varying confining pressure and bedding plane properties on shale fracture toughness is developed, and a quantitative relationship between fracture toughness and confining pressure, bedding plane angle, and density is fitted. The study reveals the complex influence of bedding properties on fracture characteristics under high stress conditions in ultra-deep shale reservoirs, potentially providing a theoretical basis for optimizing hydraulic fracturing designs and effectively controlling hydraulic fracture propagation behavior.