【Objective】In order to study the influence of mechanical properties of soil-rock mixture on the stability of tunnel excavation when tunnel passes through fault fracture zone.【Method】In this paper, discrete element software PFC 3D are used to construct a fine model of cohesive soil-rock mixture, and the mesoscopic parameter calibration is carried out in combination with the results of large-scale triaxial compression tests to carry out systematic research, and the macro-mechanical properties of non-cohesive soil-rock mixture are compared with those studied by existing scholars, so as to analyze the influence of different factors on the macro-mechanical properties of soil-rock mixture.【Result】With the increase of volumetric block proportion, the relationship between the block and the soil matrix gradually changes to the block-soil skeleton structure, and the shear strength increases rapidly; When the block orientation angle is between 0° and 90°, the shear strength of the soil-rock mixture decreases first and then increases, reaching the lowest value at about 45°; Under the action of high confining pressure, the difference of the overall movement and rotation of the block is more significant, and the block orientation angle of the block has a greater influence on the strength of the sample.【Conclusion】Regardless of the nature of the soil matrix in the soil-rock mixture, confining pressure, stone content and stone inclination angle have significant effects on the mechanical properties of the soil-rock mixture. Therefore, the construction of the fault fracture zone should be combined with the above factors for comprehensive analysis, and a reasonable advance support scheme should be summarized.