The elutriation of fine powders (Group C or A powders in Geldart’s classification) from a fluidized bed of fines-coarse particle mixtures had been investigated in a transparent column with diameter of 7.1 cm and height of 102 cm. In the experiments, a silica sand (Group B in Geldart’s classification) was used as the coarse particles, whereas several kinds of limestone powder varying in Geldart’s classification from A to C were used as fines. The elutriation rate constant of fine powders was obtained by measuring the elutriation rate of powders, and the concentration of powders in the bed at steady state. The effects of superficial gas velocity, concentration of powders in the bed and diameter of powders on the elutriation rate constant were investigated. Experimental results showed that the elutriation rate constant of powders reaches a maximum at a certain powder size corresponding approximately to the boundary between Group A and C powders, giving an indication of the different elutriation mechanisms between Group A (or B) particles and C powders. This finding is contrary to the assumption made by existing models for the prediction of elutriation rate of Group A and B particles and may be attributed to the powder cohesivity.