We have studied hydrodynamic characteristics of three-phase inverse fluidized bed. Three-phase inverse fluidized bed of this experiment is made of a transparent acrylic column of 11.5 cm inner diameter and 2 m height. Air, water and polyethylene particles were used as the gas, liquid and solid phase, respectively. We used both hydrophobic LDPE(low density polyethylene) and hydrophilic LDPE as solid phase, and distilled water as liquid phase, and air as gas phase. LDPE was chemically treated by chlorosulfonic acid to change the surface from hydrophobic to hydrophilic and then LDPE density was increased. We measured the static pressure and critical fluidization velocity, to analyze the hydrodynamics characteristics of hydrophobic/hydrophilic particles. As a result of this study, we observed that the density increased when the surface of LDPE particles was treated hydrophilically using chlorosufonic acid. As observed, the critical fluidization velocity of hydrophilic particles was decreased. But, this result is more due to density increase rather than surface modification. When we used two kinds of particles(hydrophobic/hydrophilic) together, the efficiency of the inverse fluidization was improved. This comes from the mutual aid between two factors such as density and surface property. Thus, critical fluidization velocity decreased with increasing hydrophilic particle content.