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The backfill in the stope usually forms a composite structure with the surrounding rock in order to bear pressure together to support the goaf and ensure the safe mining of subsequent ores. Based on laboratory tests and theoretical analysis, the energy and damage evolution of the rock–backfill composite materials (RBCM) are studied deeply. The results show that: (1) The <i>σ_p</i> (peak stress), <i>ε_p</i> (peak strain), and <i>E</i> (elasticity modulus) decreased with the increase of the internal backfill diameter. When the diameter of the backfill increases from 10 mm to 40 mm, <i>σ_p</i> decreases from 50.15 MPa to 18.14 MPa, <i>ε_p</i> decreases from 1.246% to 1.017%, and <i>E</i> decreases from 7.51 GPa to 2.33 GPa. The <i>U^T</i> shows an S-shaped distribution, the <i>U^E</i> shows an inverted <i>U</i>-shaped distribution, and the <i>U^D</i> first increases slowly and then increases rapidly. The <i>U^T_p</i>, <i>U^E_p</i>, <i>U^D_p</i>, <i>U^E_p</i>/<i>U^D_p</i>, and <i>U^E_p</i>/<i>U^T_p</i> decrease by 67.38%, 97.20%, 58.56%, 32.64% and 13.64% respectively, and the <i>U^D_p</i>/<i>U^T_P</i> increases by 20.93% with the increases of the backfill diameter. (2) A damage constitutive model of the RBCM is established based on the energy consumption characteristics. The damage evolution curve shows an S-shaped distribution, and the damage rate evolution curve shows an inverted U-shaped distribution. (3) The AE correlation fractal dimension decreases with the increase of the strain gradient and damage value, and the AE correlation fractal dimension presents linear and exponential functions with them, respectively. With the increase of stress, microcracks first appear and gather in the internal backfill of the RBCM, and then microcracks appear and gather in the peripheral rock, which together lead to the macro penetration failure of the RBCM.