Thermochemical thermal storage has attracted wide attentions because it has high thermal density heat storage and can realize seasonal thermal storage and long-distance transportation. The CaCO₃/CaO reaction system, as one of the most promising thermochemical heat storage materials, has problems such as particle aggregation and sintering as the number of heat storage cycles increases, and the material gradually loses its activity. To solve this problem, composite CaO materials doped with Al₂O₃ or CeO₂ were synthesized by the template method. The microstructure of the materials and the effect of chemical doping on the cyclic stability of the composite CaO materials were investigated by means of characterization tests such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and synchronous thermal analyzer (STA). The effect of chemical doping on exothermic reaction temperature range of the composite CaO materials was analyzed. The results show that, the CaO prepared by the template method has a richer pore structure and a superior cycling stability than the CaO obtained by decomposition of CaCO₃. When the doping molar ratio of CaO to Al₂O₃ is 100.0:2.5 (Ca:Al), the composite has the best cycling stability. After 30 cycles, the effective conversion rate decays by only about 7.1% from 0.70 to 0.65 and the exothermic energy density is 2 057 kJ/kg. The cyclic stability of the composite is better than that of CaO when the molar ratio of CaO to CeO₂ doping is 100.0:10.0 (Ca:Ce=100.0:10.0). It is found that doping with Al₂O₃ decreases the onset temperature of the exothermic reaction of the CaCO₃/CaO reaction system, whereas CeO₂ increases the onset temperature.