Abstract： Experiments were carried out to examine axial concentration distribution and mixing and segregation behaviour of binary solids mixtures in a three-phase fluidized bed of 41 mm I.D. and 1500 mm height under batch operation mode. Macroporous adsorption resin and rubber balls with different diameters but similar density were employed in the experiments. Multiple shutter plates and bed expansion method were used to determine axial variation of the bed properties including concentrations of particles in the binary mixture and gas hold-ups. The sedimentation-dispersion model which was employed to describe two-phase fluidized bed could be modified to describe three-phase fluidized bed. Experimental results show that the sedimentation-dispersion model could be used to describe the gas-liquid-solid three-phase fluidized bed of solid concentration distribution, and Fan's assumption was established.