Abstract: Nano-sized magnesium oxide was prepared with MgCl₂·6H₂O and NH₃·H₂O as main raw materials.Influences of five factors，such as Mg^{2 +} concentration，PEG-400 dispersant dosage，reaction temperature，aging time，and buffering agent（glacial acetic acid） dosage，on crystalline size were investigated by orthogonal test.Optimum preparation parameters were determined as follows：buffering agent dosage was 0.015 mol，Mg^{2 +} concentration was 0.4 mol/L，PEG-400 dosage was 5 mL，reaction temperature was 60 ℃，reaction time was 0 h，calcination temperature was 550 ℃，and calcination time was 2 h.Effects of single factor on the crystalline size were analyzed.Mimic paraoxon was selected to test the absorption and degradation of nano-sized MgO.Results showed that the absorption and degradation of 0.4 g nano-MgO to 1μL paraoxon reached 99.19% within 5 min.1 g nano-MgO could degrade and adsorb 194.9 mg paraoxon. 

Key words: nano-sized magnesium oxide, orthogonal test, paraoxon