To study the thermal hazard of the composite modified double-base propellant with high solid content, the thermal decomposition of GHT-1A was studied by TG, DSC, and ARC. Its mass fraction of Hexogen (RDX) is about 48.5%. The test results were compared with one double-base propellant S0 and single-compound explosive RDX. And the thermal hazard of GHT-1A was evaluated from two aspects. The TG/DSC test results show that the decomposition peak temperature of double-base component of GHT-1A is higher than that of S0, and the peak temperature of explosive components of GHT-1A is close to that of single-compound explosive RDX. The ARC test results show that, in the ideal adiabatic environment, the initial exothermic temperature for GHT-1A is 138.9℃, the adiabatic temperature rise is 1415.3℃, the time to the maximum rate is 13.8min, and the maximum pressure produced by unit mass is 13.1 MPa·g-1. The studies have revealed that, the explosion feasibility of GHT-1A is lower than that of double-base propellant S0, but higher than that of single-compound explosive RDX. And the destructive effect of GHT-1A is among the strongest. ©, 2015, Editorial Office of Journal of Propulsion Technology. All right reserved.