Nanoparticle magnesium aluminate spinel powder MgAl2O4 was synthesized by combustion method at 300◦C via combusted a stoichiometric mixture of aluminum and magnesium nitrates with malonic acid dihydrazide as a fuel following by annealing at 800, 1000 and 1200OC. The obtained samples characterized by different tools as thermal analysis (TG-DTA), X-ray diffractions (XRD), UV–Vis spectroscopy, transmission electron microscopy (TEM) and infrared spectroscopy (IR). Particle sizes with a size of 10-12.5 nm was produced within the range of 800-1200oc for 2h for each temperature. The energy gap was shifted from 3.76 at 800oc to 2.95eV at 1000oc due to the formation of high crystalline structure as result of the annealing.