The effects of 1, 4-dinitropiperazine (DNP) on the combustion characteristics and thermolysis of CMDB propellants were studied by differential scanning calorimetry (DSC) and burning rate test. Results show that the thermolysis of RDX in propellants are affected obviously by DNP, and the burning rate and pressure index of CMDB propellants decrease with the increasing of DNP content. These phenomena become more evident when the pressure is 12-18 MPa. In addition, when the DNP content increases to 20% (DN3), there is an extra thermal decomposition peak of DNP which is separated from the main exothermic peak, and there is a lower exothermic peak beside it with the pressure increasing to 9 MPa.