Abstract: An improved space-time conservation element and solution element (CE/SE) scheme with a chemical reaction models-two-step reaction model were constructed by proposing a new structure of solution elements and conservation elements based on the rectangular mesh. Numerical simulation results describe that the physical and chemical characteristics of the multi-gas phase flows such as the density of gas, velocity of wave, temperature and pressure are 6.4 kg/m³,1 580 m/s, 7 MPa and 2 560 K, respectively. The results show that the improved CE/SE scheme and the two step reaction model is easy to be implemented and high accurate for nanoparticle growth during the gas-phase detonation reaction process.