Abstract: Method of preparing highpurity nanomagnesium oxide by liquid precipitation method with lightburned magnesium oxide powder,fertilizergrade ammonium sulfate,and industrialgrade ammonium bicarbonate as raw materials and A12+A17+N2 as surface modifier was introduced.Results of single factor and orthogonal experiments indicated the optimal process conditions were as follows: volume ratio of ammonium carbonate solution to magnesium sulfate solution was about 0.8∶1,reaction time was 100 min,reaction temperature was 70 ℃,concentration of ammonium carbonate solution was 0.7 mol/L, concentration of magnesium sulfate solution was 0.7 mol/L,total amount of complex surfactant was 0.1 mL,precursor was dried at 60 ℃ for 2 h under vacuum and calcined in muffle furnace at 600 ℃ for 1.5 h to produce magnesium oxide.Highpurity nanomagnesium oxide were characterized by laser particle size analyzer,XRD,and SEM.Results indicated that the products were well dispersed with narrow size distribution and an average size of about 65 nm.Purity of magne sium oxide in products was over 99.5%.The simple process introduced can bring steady product quality and can be easily industrialized. <BR>