Thermal behaviours of graphite/potassium nitrate (C/KNO₃) with different proportion were studied by TG-DSC technique. The kinetic parameters of thermal decomposition reaction for C/KNO₃=90/10 mixture were calculated by Friedman′s method. Results show that thermal decomposition of C/KNO₃ is solid-phase reaction. At the same heating rate, propotion and the decomposition characteristics are different. At different heating rates, propotion is same but the decomposition characteristics are also different. C/KNO₃ decomposition process is very complex with three or more reactions. Activation energy of the main decomposition reaction is between 102.84~374.27 kJ·mol^-1 and the pre-exponential factor between about 3.25~10.39 s^-1.