Abstract: The“rock-coal-rock”parallel bond numerical model is established based on the particle flow code (PFC). By changing the thickness of the middle part of coal, this paper discusses the influence of different coal thickness on the mechanical characteristics and failure characteristics of combination and further analyzes the general law of combination deformation and failure process from the propagation evolution of crack extension. The results show that the failure of coal-rock combination mainly concentrates on the middle part of coal, especially at the interface between coal and rock; combination of coal and rock damage at the angle range of 45 ° to 60 ° is shear failure, and with the decrease of coal thickness, the uniaxial compressive strength and elastic modulus of combination is increased gradually; the failure process of coal-rock combination is a progressive failure process.