The liquid-solid countercurrent fluidization process in an extraction column was numerically simulated based on the particle trajectory model of Eulerian-Lagrangian method. The simulation approach was validated by previous experiments. A power function correlation was proposed for dimensionless slip velocity U-slip/U-t and hold-up fraction., and the operational zone in the countercurrent fluidization was determined. Simultaneous countercurrent fluidization of particles with different diameters was also simulated. The comparison shows that the simulation results are consistent with the calculation values from the multi-particle free sedimentation model based on non interference assumption, verifying the reliability of the approach in present work. (C) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.