Abstract: <FONT face=Verdana>Nano-sized magnesia was prepared with brine refined from commercial brine as raw material,dolomite milk obtained by calcination and slaking of dolomite as precipitant and CTAB as surfactant.Effects of reaction temperature,brine concentration,and amount of surfactant on particle size of prepared nano-sized magnesia were discussed,and the product was characterized by XRD,TG-DTA,and SEM etc..Results showed that magnesia with average diameter of 50 nm was obtained at 60 ℃,1.0 mol/L of brine,and 0.3% (mass fraction) additive amount of CTAB.Moreover,obtained nano-sized magnesia was high in purity,good in dispersion property,and has a cubic crystal structure. </FONT>