A composite phase change material was prepared with butyl stearate as phase change material and expanded perlite as adsorption medium, and then it was mixed with cement and tailings to make phase change energy storage filling body. In order to explore the strength and thermal performance of the phase change energy storage fillings, phase change energy storage fillings with different ratios of ash to sand, mass fractions, and additive amounts of mass fractions of composite phase change materials were prepared, and the strength characteristics, thermal conductivity, and microscopic characteristics of phase change energy storage fillings with different ratios were obtained by DSC, SEM, uniaxial compression test, Brazilian splitting test, and thermal conductivity test. Research results show that there were three kinds of pore structures in the phase change energy storage filling body: tiny bubbles, bonding cracks between cementing materials and composite phase change materials, and porous structures in expanded perlite. The strength of the filling body prepared with the ratio of lime to sand of 1∶6 was about 1/2 of that of the filling body of 1∶4. When the mass fraction increased from 68% to 72% at the same ratio, its intensity increased approximately linearly. The strength of the backfill gradually decreased with the increase of the additive amount of composite phase change material, but the downward trend slowed down with the continuously increase of the amount of composite phase change material. Compared with butyl stearate, the phase change temperature of the composite phase change material decreased by 1.1 ℃, the enthalpy of phase change decreased by 45.24 J/g, and the specific heat capacity remained unchanged. After adding the composite phase change material, the thermal conductivity of the phase change energy storage filling body decreased by 6.5%.