A new approach is hereby presented to study the influence of surface properties on ultrafine alumina (Al2O3) particles towards a fluidized performance by changing the ultrafine particles (Al2O3) surface hydrophobic degree. A number of variables that affects fluidization performance of ultrafine particles (Al2O3), including hydrophobicity has been studied. The minimum full fluidization velocities (U-mff), average bed pressure drop (Delta P-a), standard deviation in pressure drop (sigma(p)) and so on, has been found to depend on the hydrophobic degree, which is a function of the ultrafine particles (Al2O3) surface properties. After treatment of the ultrafine particles (Al2O3) with a surfactant, the liquid-solid contact angle on the ultrafine particles (Al2O3) raises, thus changing the interaction between the ultrafine particles (Al2O3) and also between the ultrafine particles (Al2O3) with the micro-fluidized bed wall surface. Furthermore, some changes in important parameters such as particle size (simple agglomerate size), bulk density, flow function plots, maximum wall friction angle, BET parameters and so on were also evaluated. The fluidization of ultrafine particles is attractive, if the interaction forces between the ultrafine particles (Al2O3) and also between the ultrafine particles (Al2O3) with the micro-fluidized bed wall surface can be artificially controlled. Moreover, it is possible to achieve a better fluidization performance on the ultrafine particles (Al2O3). However, more investigation is required to improve the fluidization performance of the ultrafine particles. (C) 2016 Elsevier B.V. All rights reserved.