Two mathematical expressions for calculating the kinetic parameters of exothermic decomposition reaction of energetic materials (EMs) are derived from peak temperature of DSC curves at constant heating rates based on Kooij′s formula and van′t Hoff′s formula, the corresponding numerical method for calculating the kinetic parameters are presented. The E results obtained with the two derived formulae and Kissinger′s method, Ozawa′s method, Tang′s method, Hu-Gao-Zhang method and integral isoconversional non-linear method (NL-INT) for 2,4,6-trinitro-2,4,6-triazacyclohexanone (Keto-RDX), approximate well to each other, showing that taking the value of a of 0.5 and the value of b of 0.003 are suitable for calculating the kinetic parameters by the two derived formulae.