Experimental measurements of longitudinal dispersion coefficients of liquid have been carried out in an ejector-induced bubble column operating with co-current downflow of gas and liquid. The experimental data obtained show that the hydrodynamics of the bubble column depend on nozzle diameter, liquid jet velocity and superficial liquid and gas velocities. A model with the consideration of combined action of velocity profile and the bubble motion was developed from Taylor's theory. The dispersion coefficient of bubble motion, D-b, and the characteristic factor of velocity distribution, k, depends on the nozzle diameter, fluid velocities, which give the corresponding model equations. The dispersion coefficient calculated from the model shows a good agreement with the experimental data of this investigation in the ejector-induced downflow bubble column. (c) 2005 Elsevier B.V. All rights reserved.