A direct numerical simulation of a three dimensional plane jet is carried out to study the turbulence modulation and particle dispersion in gas-solid flows. The particle motion is simulated in a deterministic way under the Lagrangian frame. The point-force approximation is used for the two-way coupling method. The effects of particle feedback on the modification of turbulence characteristics, such as the vortex structure, velocity profiles, turbulence intensity and kinetic energy, Reynolds stress tensor, and the particle dispersion characteristics are explored in detail, under the condition of different mass loadings. With the particle feedback effects, fluid vortex structures are changed greatly. The mean velocity profiles of fluid are changed in different manners in either the stream-wise or the lateral-wise directions. For the same Stokes number, the degree of modulation of turbulence depends on the mass loadings. The turbulence kinetic energy and the Reynolds stress tensor are suppressed by addition of small particles. On the other hand, the effect of two-way coupling changes the particle dispersion characteristics greatly. The concentration is enhanced due to the two-way coupling effect, and the degree of enhancement is proportional to the mass loadings. (C) 2012 Elsevier Ltd. All rights reserved.