Abstract: The axial profiles of solids concentration and particles size were studied in a rectangular gas-liquid-solid three-phase fluidized bed reactor in the presence of a special internal of multilayer shutter-like baffle.The influence of the number of shutter layers, angle of shutter to the horizontal, and gas and slurry volumetric flow rates on the axial profiles of solids concentration and particles size were experimentally investigated. The results showed that the presence of the multilayer shutter-like baffle promoted particles segregation significantly, producing two clearer layers of solids concentration and particles size above and beneath the internal if the number of baffle layers is more than 15, and that the gas and slurry flow rates had little effect on the axial profiles of solids concentration and particles size along the bed height. The mechanism behind the effect of the internal on the axial solids profile was also discussed.