Coal mining produces a large amount of coal gangue. For example, recycling coal gangue as concrete coarse aggregate not only conforms to the concept of environmental protection, but also saves sand and stone and other natural resources. In order to investigate the mechanical properties of coal gangue concrete, the multiphase micromechanical properties of coal gangue concrete were studied. Based on the meso-scale, the heterogeneous numerical model of gangue concrete is established, and the influence of various internal media on the mechanical properties of gangue concrete is studied. The results show that the mesoscopic model can well describe the mechanical properties, failure mode and internal damage evolution process of gangue concrete. The mechanical properties of gangue concrete are related to the three-phase mechanical properties. With the increase of ITZ strength, the peak stress of gangue concrete first increases and then decreases, but the residual strength tends to be the same. The improvement of ITZ mechanical properties has little effect on the failure mode of gangue concrete and the distribution and propagation of macro-cracks. Increasing the strength of cement mortar can increase the peak stress and brittleness of coal gangue concrete. The strength of coarse aggregate increases the peak stress of concrete. When, the peak stress of concrete can be effectively increased. When, the peak stress growth rate will decrease rapidly. The brittleness of concrete can be improved by increasing the strength of aggregate.