From the perspective of building functional materials, phase-change ceramics were prepared by sintering method and vacuum adsorption method using water-based cuttings and fly ash as raw materials, and the effects of sintering temperature and raw material ratio on the properties of ceramics were explored. Then, the samples before and after the adsorption of ceramics were characterized by physical and chemical analysis. Finally, the phase-change ceramics were applied to the mortar to explore the improvement of insulation performance of the envelope structure. The results show that when the ratio of water-based cuttings to fly ash is 4:6 and the sintering temperature is 1140 ℃, the performance of ceramite is the best. The specific surface area of the ceramic particle is the key factor affecting the adsorption of polyethylene glycol (PCM), and the phase transition will occur at about 28 ℃, which meets the requirement of adjusting the room temperature. The thermal conductivity of the phase-change ceramite mortar is about 1/3 of that of ordinary ceramite mortar and ordinary mortar, showing the excellent thermal insulation and low density properties of the phase-change ceramite mortar.