Abstract: Deep coal mining is confronted with complex geological conditions. To reveal the mechanical response behavior and energy evolution characteristics of coal and rock strata under deep true triaxial stress states, true triaxial loading tests were conducted on pure coal, sandstone, and composite coal-rock under different intermediate principal stresses. The results show that the composite coal-rock has a stronger plastic deformation capacity and a smaller post-peak stress drop. The dissipated energy of the coal sample increases significantly after the peak, while that of the sandstone starts to accelerate in the plastic stage. The composite coal-rock combines the characteristics of both, being close to sandstone at low stress and close to coal at high stress. The fluctuation peaks of G_e and G_d of the coal sample are near the strength peak, and increasing σ₂ reduces the amplitude. The fluctuation peak of the sandstone is in the yield stage, but σ₂ has a weak influence on it. The post-peak fluctuation amplitude of the composite rock is gentle but the amplitude is high, and increasing σ₂ significantly suppresses its post-peak amplitude. The post-peak elastic energy release has a greater impact on the brittleness index than the pre-peak elastic energy storage. The coal sample is mainly penetrated by a single main crack and is less affected by the change of σ₂. The sandstone has a complex fracture network at low σ₂ and the failure tends to simplify at medium and high stress. The fracture network of the composite coal-rock is the most complex, and increasing σ₂ promotes the change of crack propagation direction.