Hydrodynamic characteristics, such as pressure drop, bed expansion and phase holdup, have been investigated in a three-phase inverse fluidized bed reaction process whose diameter and height are 0.152 m and 2 m, respectively. Experiments were carried out by using low density polypropylene(s=877.3kg/m(3)) and polyethylene(s=966.6kg/m(3)) beads. The data of bed expansion and static pressure drop were used to determine the minimum fluidization velocity and individual phase holdups. It has been found that the bed porosity and liquid holdups increase with increasing gas and liquid velocities. The effects of gas velocity are more important on the bed expansion than these of liquid velocity in a three-phase inverse fluidized bed.