The effects of different ballistic modifiers (Cr2O3.CuO, ammonium oxalate, and carbon fiber) on the thermal decomposition behavior of RDX/AP/HTPB propellant are studied using pressure DSC. The burning rates of the four propellants are determined by using a Crawford bomb. The results show that in the presence of Cr2O3.CuO or carbon fiber, the peak temperatures of the decomposition of RDX and AP decrease. The enthalpy of decomposition and the burning rates and the number of the exothermic decomposition peak of two kind of RDX/AP/HTPB propellant containing Cr2O3.CuO and carbon fiber increase. When ammonium oxalate is added into the RDX/AP/HTPB system, the peak temperature of decomposition of RDX shifts upwards, and the enthalpy of decomposition of RDX/AP/HTPB propellant decreases, and the burning rate reduces. These facts indicate that the relationship between the effect of the ballistic modifiers on the burning rate and that on the thermal behavior of RDX/AP/HTPB propellant is close. (C) 2003 Elsevier B.V. All rights reserved.