A numerical model for simulating the buringing rate and pressure of NEPE propellant was developed based on the chemical structure of component, thermal behavior and combustion characteristics. Burning rates of three NEPE propellant formula containing the aluminum were calculated and compared with the experimental results to study the effects of aluminum particle content and particle size on the propellants combustion characteristics systematically. Results show that the errors of burning rate of NEPE are within±15% between calculated and experimental results, and 70% in which is within±10%. The model predicts there is a low pressure exponent under 5 MPa by using 1-3 μm fine aluminum powder.