Particle dispersion behavior of dense gas-particle flows in a downer affected by gravity environment is numerically simulated using an Euler-Euler two-fluid approach incorporating unified-second-order-moment two-phase turbulent models and kinetic theory of granular flows (USM-theta). Anisotropy of gas-solid two-phase stress and the interaction between two-phase stresses are fully considered by two-phase Reynolds stress model and the transport equation of two-phase stress correlation. The flow behavior of particles in a downer of Wang et al. (1992) [27] experiments is predicted under earth gravity, lunar gravity and microgravity environment. Simulation results of particle concentration and particle velocity are in good agreement with measurement data under earth gravity environment. Comparison earth gravity to lunar and microgravity condition, peak value of particle concentration is shifted to near center region and axial particle fluctuation velocity is larger than that of approximately 3.0 times. Particle temperature, particle heterogeneities dispersion and particle-particle collision are weakened due to decrease gravity. Furthermore, roles of particle and gas kinetic energy in particle-fluid system are alternated. Both particle kinetic energy and gas kinetic energy are greater than ones under earth gravity conditions. (C) 2010 Elsevier B.V. All rights reserved.