Abstract: Axial compression tests were carried out on 19 binary and ternary combined bodies with different coalrock ratios and combinations to investigate the mechanical properties and failure mechanism. The mechanical properties of the combined body are analyzed,including compressive strength,elastic modulus,pre-peak energy and impact energy index. Based on the theoretical analysis of the interaction model of coal-rock combined body,the instability failure mechanism of coal-rock combined body is explored,and the energy transfer mechanism inthe failure process of coal-rock combined body is studied from the different failure patterns of the coal-rock combined bodies. It is found that the compressive strength of the combined body is between the compressive strength of each component,and tends to approach the compressive strength of the weak component,which increases with the proportion of the fine sandstone. The elastic modulus of the combined body increases with the proportion of the fine sandstone. The greater the elastic modulus of rock,the greater the elastic modulus of the combined body. The combined bodies with coal components accumulates less energy before the peak stress,and the combined bodies composed of fine sandstone and coarse sandstone accumulates more energy before the peak stress,and the pre-peak energy of the combined body increases with the proportion of fine sandstone. The impact energy index of the assemblage is linear with the proportion of fine sandstone,which increases with the proportion of fine sandstone. The composition of fine sand has a great influence on the compressive strength,pre-peak energy and impact energy index of the combined body,and plays a decisive role in the mechanical properties and impact effect of the combined body,and deduces the formula for calculating the elastic modulus of the coal-rock combined body. The law that the elastic modulus of the combined body increases with rock proportion is revealed theoretically. The mechanical model of the coal-rock combined body is constructed,and the instability and failure mechanism of the combined body is analyzed. The energy transfer mechanism in the failure process of coal-rock combined body is discussed. The research results provide references for the study of failure pattern,mechanical properties and instability mechanism under the interaction of coal and rock mass in the process of coal resources mining.