Thermal decomposition and combustion characteristics of nitroguanidine(NQ) are analysed.The NQ decomposition hypothesis about the primary stage of combustion is proposed,and the burning rate formula and pressure index formula of NQ propellant are derived.The NQ propellant burning characteristics from 0 MPa to 400 MPa are numerically modeled and calculated, result are in good agreement with the experimental data. The accurate calculated results show that the pressure index decreases at the middle and high pressure region with the addition of NQ to the double base propellant.The reason of low pressure in- dex and the possibility of NQ as a buming rate modifier in nitramine (RDX and HMX) pmpeUant are discussed.