For the problem of micron-sized α-alumina powders dispersed in water suspension,the single factor test was used to study the effect of milling time,ultrasonic time on the dispersion of α-alumina powders in water suspension. The orthogonal test was used to study the effect of dispersant kinds,dispersant concentration and p H of suspension on the dispersion of micron-sized α-alumina powders. Absorbance of suspension was used to evaluate the dispersion of α-alumina powders. The results show the optimal dispersing conditions are that the milling time is 40 min,ultrasonic time is 20 min,mass fraction of sodium tripolyphosphate is0.5% and p H of suspension is 10.