To improve the utilization efficiency of renewable energy and adaptability of composite materials, a new mineral-based composite phase change material (Ag-Mica/CNF/PW) was designed and prepared by chemically modifying natural mica, attaching silver nanoparticles to the mica surface as functionalized support material, and using paraffin wax as the phase change functional medium. As expected, the thermal conductivity of the composite phase change material (CPCMs) increased significantly to 0.9 W/m k, which was 330.1% higher relative to pure paraffin. With the addition of silver-modified mica, the volume resistivity of CPCMs reached 11.9 × 1012 Ω cm. The relative enthalpy efficiency achieved 104.8%, and the photothermal conversion efficiency reached 91.3%, proving that the silver-modified mica-based CPCM was successful and feasible. The heat resistance index of CPCMs was 137.2 °C, and the enthalpy loss rate after 50 cycles was only 0.7 %, indicating that CPCMs have excellent thermal stability. The designed CPCMs are a promising candidate for developing thermal storage and building thermal management, electrical insulation and solar energy conversion.