The dielectric characteristics of the solid fuels have close relation with gasification process. Electrochemical impedance spectroscopy (EIS), is applied for measuring the dielectric characteristics of solid carbon fuels in catalytic and non-catalytic gasification systems. Compared with kinetic experiments at different gasification temperatures (775, 800 and 825 degrees C) for both catalytic and non-catalytic gasification, EIS spectra is proved to be an effective method to characterize the carbon gasification reaction characteristics in situ with high sensitivity, especially at low carbon conversion ratio. An elementary reaction model for potassium catalyzed carbon gasification combined with a dielectric mixture equation for the simulation of complex permittivity is developed. The modeling results agree well with the experimental data. The dielectric property of catalyzed solid carbon fuels provided by EIS reveals that the polarization intensity contains effective information of gas adsorption and heterogeneous chemical reaction. EIS can possibly be applied as a new methodology in investigating the catalytic carbon gasification reaction and transport processes. (C) 2014 Elsevier Ltd. All rights reserved.