In this study we have made ourselves to better understand the characteristics of unsteady particle and gas flows. The discrete phase method (DPM) was used to simulate unsteady particle and gas flows, and a discrete random walk model was chosen to record the unsteady particle tracking. Numerical results were obtained for comparison with the results of experimental pressure measurement and particle visualization. It was observed that the shock wave propagation agrees well with the experimental results from the numerical simulations. The particles were accelerated at the exit of the micro shock tube due to reservoir pressure induced by the reflected shock wave. Both the sonic and supersonic nozzles were under expanded at the end of the micro shock tubes. The particle velocity was calculated to be less than the gas velocity, which is a result of the greater drag of the injected particles.