The calcium looping (CaL) process is a promising CO₂ capture technology based on a reversible reaction, CaO(s) + CO₂(g) ↔ CaCO₃(s), and the forward and reverse directions of this reaction are often referred to as carbonation and calcination. Although CaO-based sorbent has the advantages of abundant reserves, low cost, and high theoretical capacity of CO₂, it is limited by significant sintering of CaO grains over carbonation/calcination cycles, resulting in a rapid decline in CO₂ capture performance. As an essential part of CaL technology, the CaCO₃ calcination stage has a decisive influence on the sintering degree of CaO grains. In this work, a systematic understanding of fundamental aspects of the CaCO₃ calcination is reviewed. The effects of calcination reaction conditions on the sintering of CaO grains and the resulting decline in CO₂ capture performance during the cyclic operation were discussed. A number of efforts to reduce the calcination reaction temperature, thus slowing down CaO grains sintering, have been summarized, such as decreasing CaCO₃ crystallinity, doping CaCO₃ with alkali/alkaline earth salt, reducing CO₂ absolute pressure, injecting steam, as well as in situ converting CO₂. Finally, the future development trends for the above strategies to reduce the CaCO₃ calcination temperature are also recommended. We hope this work can help and inspire researchers to make breakthroughs in this field.