Generally, a combination of one-stage paddle drying and two-stage flash drying is used to dry alumina micropowder. The first stage paddle drying will dry the attached water to less than 15% of the semi-finished product, and then use the function of the second stage rotary flash drying that can both dry and crush materials to dry the aluminum hydroxide powder of the semi-finished product with attached water to less than 0.15% without agglomeration, and then reach the qualified standard of micro powder.