Abstract: The red-bed soil-rock mixture(RB-SRM)has been widely used in the subgrade filling of highways and railways in Sichuan-Chongqing region. Studying the strength and particle crushing characteristics of RB-SRM can provide theoretical support for the rapid and safe construction of subgrade in the region. Aiming at the insufficient applicability of the existing particle size distribution evaluation method to the SRM, we proposed the relative content of intermediate particle sized blocks(C_m), and put forward four levels. We chose the RB-SRM of Sichuan Basin as the material. After comparing the laminated shear test and the large-scale direct shear test, we discussed the effect of particle size distribution on the strength and particle breakage of RB-SRM in combination with the sieving test. The results show that the shear plane of the laminated shear test is not fixed by human, and the influence volume of the shear band is much larger than the large-scale direct shear test. The shear strength of RB-SRM obtained by the laminated shear test is lower than that of the large-scale direct shear test. And the higher the normal stress, the greater the difference between the strength. C_m has a significant effect on the strength and particle breakage of RB-SRM. With the increase of C_m, the cohesion decreases first and then increases, the internal friction angle increases first and then decreases, and the shear strength increases first and then decreases. All of them have the optimal value at C_m=0.543. At this position, the positive effect of friction and reorientation on the strength of particles is much larger than the negative effect of occlusion weakening, and the shear stress increases again. After the laminated shear test, the content of large, medium sized blocks decreases, while the content of soil increases. The content of small sized blocks decreases when C_m≤0.343, and increases when C_m≥0.343. With the increase of normal stress and C_m, the relative particle breakage rate decreases first and then increases, which has the minimum value at C_m=0.343.