In order to further reveal the internal relationship between the impact dynamic characteristics of coal and rock mass and the energy evolution, the true triaxial test system is used to carry out loading and unloading tests on coal and rock samples with different thickness ratios of coal samples. The energy absorbed by the samples in the process of external force loading and unloading deformation to instability failure is calculated through integral calculation. The energy evolution characteristics of each sample in different stages and directions in the test process are compared and analyzed, The energy evolution law is analyzed based on the strength characteristics and failure crack characteristics of the unstable failure. The results show that: ①With the increase of the proportion of coal sample thickness, the cumulative energy absorbed during the instability failure of the sample showed the characteristics of an up-convex parabola that first increased and then decreased, which was positively correlated with the evolution characteristics of the failure crack characteristics of the sample, indicating that the cumulative absorption energy of the coal rock mass was positively correlated with the kinetic characteristics of its instability failure; ②With the increase of thickness ratio of coal sample, the strength of sample decreases gradually, and there is no obvious positive correlation with the evolution law of cumulative absorbed energy of sample. Therefore, the essence of failure and instability of coal and rock mass can be better revealed by energy analysis and studying its regulation law than by analyzing the failure strength; ③ Under the condition of different medium properties of coal and rock mass, the energy accumulation caused by the original rock stress and the energy increment caused by the later external force disturbance can be the dominant cause of its impact failure. This further confirms that under certain conditions, high static load and dynamic and static load can induce rock burst; ④The external force loading is the essential source of energy absorption, and the energy absorption in a single direction is also related to the external force unloading in the structural plane and other directions. Therefore, the fundamental method to restrain energy accumulation is to unload the external force, and the linkage effect caused by the change of coal and rock mass structure and external force in other directions should also be considered. The research results have certain theoretical significance for exploring the mechanical characteristics of coal rock mass impact, and can provide theoretical and technical support for the prevention and control of rock burst.