Critical gas velocity for complete solid suspension is studied experimentally in a slurry-bubble column with a draft tube at the bottom, of which the height was less than half of gas-liquid dispersion height. Experiments on the critical gas velocity are carried out with variation of diameters of bubble column and draft tube, length of draft tube, kind of solid particle, and viscosity of liquid phase. Although the tendency of the effect of the above mentioned variables on the critical gas velocity agrees with the previous work where the draft tube has approximately the same height as the gas-liquid dispersion height, the estimated values by the previous work do not coincide with the data. The empirical equation for the critical gas velocty is presented by correlating the present data.