The model-free and model fitting approaches have been applied to the data for non-isothermal decomposition kinetics of SiO2 surface coated calcium carbonate as well as the reference. The decomposition mechanisms as revealed by computation show great differences. Nano-sized reference samples decompose according to the contracting volume mechanism (R-3) While the surface SiO2 coated calcium carbonate shows the one-dimensional diffusion (D-1) behavior, possibly because of the framework constituted by surface SiO2 layer hinders the diffusion of the dissociate products into the outer atmosphere. At the mean time, the activation energy is increased by 30-35 kJ/mol in the process controlled by diffusion compared with the reference. However, the usual model fitting approach may also yield highly uncertain values of Arrhenius parameters when applied to non-isothermal data, so that a combination of master plot method and model-free kinetic approaches based on the isoconversional method that yields the dependencies of the activation energy on the extent of the conversion were also used to evaluate the credulity of the kinetic parameters achieved by model fitting methods.