Abstract: Analysis was made on determination of particle size of superfine alumina powder by Marvan MS2000 with Hydro 2000MU.Influence of factors,such as ultrasound intensity,background,surfactant,absorption rate,pump speed,and obscuration,on dispersion performance of the powders was mainly investigated.These tests confirmed the basic experiment conditions of superfine alumina powder that intensity of ultrasound was 15,absorption rate was 0.1,pump speed was 2 850 r/min,obscuration was 10%,4 mL sodium hexametaphosphate with mass fraction of 2% and 2 drops of sodium dodecylbnzene sulfonate with mass fraction of 2% were added to the dispersant of water.This method has excellent accuracy and high data reproducibility.<BR>