A modified direct simulation Monte Carlo (DSMC) method is proposed in the present paper for obtaining the particle motion behavior which is of essential importance for research of the transfer processes in a gas-particle two-phase impinging streams (GPIS). In GPIS, the particle concentration distribution is extremely nonuiform. The particle collisions play an important role in the particle motion behaviour inside the impingement zone with high particle concentration, nevertheless, the interactions between gas phase and particle phase play an important role outside the impingement zone. And the volume of the impingement zone is relatively small, and the time required for a particle to pass through this zone is very short. According to these characteristics of multiple spatial scale and multiple time scale, the DSMC method is modified to be more suitable to the numerical study of GPIS. This modified DSMC method is not restricted to flow field cells in the calculation of particle motion and collisions, and the particle time step in this method is adaptive and calculated using local particle parameters. The algorithm and numerical solution method of this method are also given in this paper. The predicted results of the particle motion behavior in GPIS are in reasonable agreement with the experimental data, which indicates the validity of the present method. (c) Elsevier Ltd. All rights reserved.