Abstract: In order to explore the mechanical response law of different coal rock proportion combinations under true triaxial load, the cube specimens with different combination methods were prepared. The true triaxial test was carried out with the field measured stress evolution as the loading path to explore the mechanical response and deformation characteristics of different coal rock proportion combinations under the stress path, and the pure coal and rock samples were added as the reference for comparative analysis. The results show that the strength, elastic modulus and deformation resistance of coal and rock samples under true triaxial compression are significantly higher than those under uniaxial compression. The mechanical parameters and peak strain of coal rock combination are between coal sample and sandstone sample, and the strength and elastic modulus of specimen are negatively correlated with the proportion of coal thickness. However, with the increase of coal seam thickness, the decreasing trend of the two is not the same. The elastic modulus decreases almost in equal proportion with the increase of coal seam thickness, while the decreasing rate of strength with the increase of coal seam thickness gradually decreases. The reason is that the heterogeneity of coal is more prominent than that of sandstone. The peak strain does not change monotonously with the increase of coal seam thickness. The peak strain of ternary combination is larger than that of binary combination. Under triaxial loading, the difference between mechanical parameters and deformation characteristics of coal rock and rock coal composite specimens is very small, which is considered to be caused by the heterogeneity of coal rock material.