Abstract: To explore the longitudinal hydraulic fracture propagation mechanism in ultra-deep shale reservoirs, the influence of high stress and bedding properties on shale fracture characteristics was systematically analyzed. Initially, shale mechanical parameters were obtained through triaxial compression experiments. Subsequently, a three-point bending numerical model of a semi-circular shale plate with confining pressure was constructed using the particle discrete element method to simulate the shale fracture process under various conditions. The numerical simulation results demonstrate that increasing the 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. 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, the quantitative relationship of fracture toughness with confining pressure, bedding plane angle, and density was fitted, and a quantitative chart illustrating the impact of varying confining pressures and bedding plane properties on shale fracture toughness was developed. The results reveal the complex influence of bedding properties on fracture characteristics under high stress conditions in ultra-deep shale reservoirs, providing a theoretical basis for optimizing hydraulic fracturing schemes and effectively controlling hydraulic fracture propagation behavior.