The disclosure relates to a phase change thermal storage ceramic having high service temperature and improved utilization rate and utilization efficiency of heat. It is prepared at a low cost with a simple, easy-to-industrially-realized method. A mixture is obtained by mixing and stirring evenly 50-85 wt % of fused mullite powder, 10-45 wt % of pretreated aluminum-silicon alloy powder, and 3-8 wt % of ball clay. A ceramic body is formed by press molding the mixture at 80-150 MPa. The ceramic body is cured at 25-28° C. and a relative humidity of 70-75 RH for 24-36 h, dried at 80-120° C. for 24-36 h, and held at 1,100-1,300° C. for 3-5 h to prepare the phase change thermal storage ceramic. The pretreated aluminum-silicon alloy powder is prepared by holding aluminum-silicon alloy powder in water vapor at 0.02-0.20 MPa for 0.5-3 h to impregnate in an alkaline silica sol and drying the impregnated powder.