This paper proposes a two-dimensional numerical method for gas-particle two-phase free turbulent flow based on a vortex in cell method. The present method simultaneously calculates the behavior of vortex element and the particle motion by the Lagrangian approach. The change in the vorticity of the vortex element owing to the particle is simulated through the algorithm for a vortex method proposed by the authors in the prior study. The present method is also applied to simulate a gas-particle two-phase plane mixing layer to demonstrate its validity and applicability. To examine the effect of the particle diameter d, two kinds of particles with d = 72, 135 mum are loaded. The particle mass loading ratio ranges from 0 to 0.7. The simulation revealed that the method allows the computation with less CPU time than the vortex method. The gas flow field and the particle motion were favorably compared with those obtained by using the vortex method. (C) 2004 Elsevier B.V. All rights reserved.