Nano-structured MgO and MgO:Al powders were prepared in a continuous micro drop fluidization scheme with one step process. The optical and magnetic properties of MgO: Al powders were developed effectively by providing the micro drops with plausible contacting with micro bubbles by means of fluidization during the formation of powders. The micro shear force generated at the surface of micro drops during the formation stage could affect the defect-induced opto-magnetic properties of the MgO: Al powders. The doping effects of small amount of Al3+ (0.5 at.%) ions into MgO lattice could be enhanced considerably by adjusting the reaction condition such as flow rate of micro bubbles (U-MB). The bandgap energy became narrow and the surface area increased by the doping of Al3+ ions, with increasing U-MB. Both vacancies of oxygen and Mg2+ which were generated due to the doping of Al3+ ions in the micro drop fluidized reactor could affect the magnetic properties of MgO: Al, and the value of saturation magnetization of MgO: Al powders increased effectively with increasing U-MB. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.