The fluidization behaviors of ultrafine particles were investigated in an acoustic fluidized bed with one type of micron particles and two types of nanoparticles. With the assistance of sound wave having low sound frequency and high sound pressure level, the micron and nanoparticles can be fluidized smoothly with fluidization behaviors similar to those of Geldart Group A particles. It has been found that increasing sound frequency leads to a reduction in minimum fluidization velocity, and then to an increase in minimum fluidization velocity. At the same sound frequency, the fluidization quality of nanoparticles improves significantly with increasing sound pressure level (100-103.4dB). In addition, a thorough investigation indicates that sound wave configuration have an influence on fluidization process of ultarfine particles. Experiments show that both Sine wave and Triangle wave can enhance fluidization quality of ultarfine particles. (c) 2006 Elsevier B.V. All rights reserved.