The existing kinetic models often consider the influence of a single factor alone on the chemical reaction and this is insufficient to completely describe the decomposition reaction of solids. Therefore, the existing kinetic models were improved using the pore structure model. The proposed model was verified using the thermal decomposition experiment on calcium carbonate. The equation has been modified as fα=n1−α1−1n−ln1−α−1m1−ψln1−α12. This led to the conclusion that the pore structure, generated during the thermal decomposition of calcite, has an important influence on the decomposition kinetics. The existing experimental data show that the improved model, with random pores as the main body, reasonably describes the thermal decomposition process of calcite.