The stability in the energetic materials＇ thermal decomposition reaction is developed from both transient mass and heat transfer equations simultaneously. The derived equation is the sufficient and necessary condition for the reaction system＇s stability, which was expressed as: phi < (beta theta + 1)(2)/(1 - x)(n) [n phi(1 - x)(n-1) + exp(-theta/beta theta + 1)] In this stability equation, a modified Semenov number phi is the expressed function of three kinetic parameters, i.e., n, phi and beta and two variables, i.e., x and theta, respectively. A reaction system is stable if its evaluated modified Semenov number satisfies this stability criterion. In the case of the minimum modified Semenov number phi(m), we can deduce the stability equation at critical condition as beta(2)theta(c)(2) + 2 beta[1 + eta beta/n(1 - x)]theta(c) + 1 + eta/n (1 - x)(2 beta - 1) = 0 The criteria of stability for the explosives TNT, RDX, PETN and HMX were evaluated using this formula, which was expressed theta(c) as function of x at given n, eta and various beta as parameters.