Characteristics of particle flow in standpipes of a 10cm I.D. ×120cm high fluidized bed were investigated. The standpipes used in this experiment were vertical overflow and vertical underflow standpipes. Sand particles and polyethylene powders were employed as the bed materials. The effects of standpipe diameter, gas velocity and particle properties on the solid flow rate were determined. The experimental results showed that the flow behaviors of solids through the overflow and underflow standpipes are different with variations of operating conditions. For both standpipes, the mass flow rate of solids was strongly dependent on the standpipe diameter. For the overflow standpipe, the increase of gas velocity increased the solids flow rate. But for the underflow standpipe it decreased the solids flow rate. From the measured pressure drops, solid fractions in the standpipes were determined by the momentum balance. The obtained experimental data of solids mass flow rate were well correlated with the pertinent dimensionless groups for underflow as well as overflow standpipes. Characteristics of particle flow in standpipes of a 10cm I.D. ×120cm high fluidized bed were investigated. The standpipes used in this experiment were vertical overflow and vertical underflow standpipes. Sand particles and polyethylene powders were employed as the bed materials. The effects of standpipe diameter, gas velocity and particle properties on the solid flow rate were determined. The experimental results showed that the flow behaviors of solids through the overflow and underflow standpipes are different with variations of operating conditions. For both standpipes, the mass flow rate of solids was strongly dependent on the standpipe diameter. For the overflow standpipe, the increase of gas velocity increased the solids flow rate. But for the underflow standpipe it decreased the solids flow rate. From the measured pressure drops, solid fractions in the standpipes were determined by the momentum balance. The obtained experimental data of solids mass flow rate were well correlated with the pertinent dimensionless groups for underflow as well as overflow standpipes.