The high-temperature firing technology is one of the three major breakthroughs in the history of China’s ceramic development. Therefore, firing temperature measurement for ancient ceramics has long been one of the core features in the field of scientific research on ancient ceramics. However, the existing method systems generally have problems, such as large measurement errors and unclear mechanisms. In view of this, based on the thermal expansion method for temperature measurement, a series of standard samples was prepared by fully considering the differences in composition, structure and properties of ancient porcelain bodies fired in north and south China. The relationship between the “turning point” of the thermal expansion curve of porcelain body and the chemical composition and firing temperature of the body was revealed, and the influencing factors and mechanism of the curve were deeply analyzed. On this basis, the Al₂O₃ content and sintering state itself were determined to be the key technological parameters that affect the temperature measurement using the thermal expansion method.