Magnesium oxide (MgO) with different morphology were prepared by calcining precursors (magnesium hydroxide MH). The precursors were synthesized from industry lightly calcined powder (MgO content of 80-93%) by ammonia circulation method. The structures of MH and MgO were characterized by scanning electron microscope and laser particle size analyzer. The crystal growth mechanism of MgO precursors were simulated by materials studio. The experimental results showed that the MgO had the same morphology with their precursors. The adsorption of SO42 can significantly increase the particle size of precursors, and its D-50 reached 2.05 mu m. After adsorping Cl-, the exposure proportion of planes (001) and (101) was reduced, and the morphology of MH more easily grow to be uniform bulk crystal. The activity of MgO (CAA) produced with MgCl2 was 150085 by the citric acid method, which was higher than other MgO produced with Mg(NO3)(2) and MgSO4. (C) 2016 Published by Elsevier B. V. on behalf of The Society of Powder Technology Japan. All rights reserved.