Under the action of an acoustic field, the fluidization behavior of 5-10 nm SiO2 nanoparticles, with and without surface modification, was investigated. In a packed bed, the sound wave energy has a significant influence on the compact ratio of the bed. Experimental results indicated that the bed of nanoparticle agglomerates can be fluidized smoothly with the assistance of an acoustic field, and the minimum fluidization velocity is initially reduced dramatically with increasing sound frequency and then rises with increasing sound frequency. Under the same experimental conditions, the minimum fluidization velocity of 5-10 nm SiO2 nanoparticles is greater than that of 5-10 nm SiO2 nanoparticles with surface modification. The collapse of the bed demonstrates that SiO2 nanoparticles, surface modified using organic compound, have longer minimum collapse times than SiO2 nanoparticles.