compared with that of first grint and second bake, the largest advantage of this technique is great energy consumption reduction. the reason lies in , great plaster stones are ground into powders with diameter less than 0.2 mm, which increases the specific surface when calcining, enlarges contact area with heat medium , improves calcining heat exchange effciency and lowers energy consumption greatly, the disadvantages are three powder pollution position in technical process, which shall be solved with dustremoving equipment.