Abstract: Effect of different magnesium salts on the morphologies of MgO crystals was investigated.The precursors ［Mg（OH）2］with different morphologies were synthesized by employing three kinds of magnesium salts as raw materials and NH3（g） as precipitant，and then different morphologies of magnesium oxide（MgO） crystals by calcining the precursors. Scanning electron microscope（SEM），X-ray powder diffraction（XRD），TG analyzer，and laser particle size analyzer were employed to characterize the products，and citrate method was used for determination of magnesium oxide activities.Results indicated that the morphologies of MgO crystals were tetragonal massive，flake，and flower spherical with the raw materials of MgCl2·6H2O，Mg（NO3）·6H2O，and MgSO4，respectively.By means of the study on activities of magnesium oxide with dif- ferent morphologies prepared under different calcined conditions，it was concluded that magnesium oxide activity was  the highest under the heating rate of 10 ℃/min  to 600 ℃ for 2 h.Different morphologies of magnesium oxide under the same calcination condition had different  activities: tetragonal massive>flake>flower spherical.

Key words: MgO, activity, morphology