Experiments by TA2100 and STA409 C/3/F derived different kinetic parameters for same reaction. The difference changed greatly with sample load, due to mass transfer. A model was built to describe the influence of intraparticle, interparticle, and external diffusions on the thermogravimetric process. Model analysis showed that the influences of three diffusions were determined by adjustable parameters (R-p/r(e), e, e(L - e), and T) once the reaction was set and became significant with the increases in R-p/ r(e), e, e( L - e), and T. These influences can be figured out by numerical simulation. For carbon black oxidation, when the particle size was small (R-p/r(e) < 139.3), the sample layer was thin (e < 0.3 mm), and the crucible height was short (L < 2 mm), the influences of diffusions can be neglected. A data process method was presented to eliminate the influence of diffusions and the thermogravimetric experimental data by STA409 C/3/F were reprocessed and consistent kinetic parameters were obtained.