Abstract: Variation in coal-rock thickness is a common geological condition in coal mining, which not only increase the technical difficulty of extraction but may also trigger dynamic disasters such as rock burst. Effectively revealing the rock burst mechanisms associated with coal-rock thickness variation is crucial for engineering design and disaster prevention. To this end, uniaxial loading tests were conducted on coal-rock composite bodies with impact tendency at varying thickness ratios. The coal thickness effect on mechanical properties such as peak strength, peak strain, and equivalent elastic modulus was analyzed through comparative analysis of experimental and theoretical results. A multi-index system of energy evolution was established to analyze the coal thickness effect on energy storage limit, failure energy consumption, storage efficiency, dissipation efficiency, and energy conversion efficiency from the perspective of structural and energy co-evolution. Acoustic emission monitoring was utilized to analyze the energy-frequency evolution characteristics across different loading stages. The RA-AF crack classification criterion, optimized using a Gaussian mixture model, was employed to quantify the coal thickness effect on failure modes. By integration of the fractal dimension D and the acoustic emission b-value, the precursory characteristics of early-stage damage and imminent instability were identified. The coal thickness effect on the failure warning threshold and early warning window was quantitatively assessed. A mechanical model of coal-rock thickness variation at the engineering scale was developed to reveal the disaster-inducing mechanisms associated with thickness variability and to derive engineering insights for disaster prevention and control. The results indicate that:With increasing coal thickness ratio, both the peak strength and equivalent elastic modulus of the specimens exhibit nonlinear decreases, while the peak strain shows a nonlinear increase; As the coal thickness ratio increases, the energy storage limit, failure energy consumption, and storage efficiency all exhibit nonlinear decreases, while failure energy dissipation efficiency and energy conversion efficiency increase nonlinearly; As the coal thickness ratio increases, the proportion of tensile failure modes decreases linearly, the risk of rock burst is reduced, the failure warning threshold increases nonlinearly, and the early warning window becomes shorter; The disaster-inducing mechanism of coal thickness variation results from the combined effects of vertical energy potential differences and horizontal energy gradient effects in the strata. Based on the analysis of rock burst risk in the direction of seam advancement and engineering practice, it is suggested that advancing from thinner to thicker coal zones is preferable.