Abstract: The thermal decomposition behavior of composite modified double-base(CMDB) propellant containing cyclotrimethylene trinitramine(RDX) was studied via a Calvet microcalorimeter at five different heating rates. The activation energy(E) and the pre-exponential factor(A) of two obvious exothermic processes were obtained by Kissinger’s method and Ozawa’s method. The entropy of activation(ΔS^≠), the enthalpy of activation(ΔH^≠), and the free energy of activation(ΔG^≠) of the first stage were calculated. To evaluate the thermal hazard of the RDX-CMDB propellant, the critical temperature of thermal explosion(T_b), the self acceleration decomposition temperature(T_SADT), the adiabatic decomposition temperature increment(ΔT_ad) and the time-to-explosion of adiabatic system(t) were presented as 145.3 °C, 138.15 °C, 1634 K and 583.71 s(n=0) and 586.28 s(n=1), respectively.