Euler-Lagrange model was used to solve two-phase flow and simulation in micro pulse solid rocket motor, a three-dimension physics model and a mathematical model of motor flow field were established, the effects of pure gas and particles diameters from 1 ~ 50 µm on pulse solid rocket motor were studied. The numerical simulation result show that the pure gas inertia results in asymmetric distribution of gas-phase field, the distribution of particles is different from different diameter. In the same mass proportion, the bigger the particle is, the less diathermancy and baffle on gas-phase is: The smaller the particle is, the better the flowing property becomes, the more obvious the exchange of energy and kinetic energy with gas-phase is.