Magnesium silicon nitride (MgSiN2) powder was prepared by carbothermally reducing a magnesium metasilicate whose chemical composition corresponded to MgO . SiO2 or MgSiO3. About 0.2 g of the powder mixture of magnesium metasilicate and carbon (C) with the molar ratio of C to MgO . SiO2 equal to 6.0 was heated at 1250 degrees C for 7 h in nitrogen atmosphere. The crystalline phase of the carbothermally reduced powder was only MgSiN2. The residual carbon could be removed by heating the powder at 600 degrees C for 1 h in air. The yield of MgSiN2 powder was similar to 70%. The resulting powder contained 3.22 mol% oxygen. The primary particle sizes were ranging from 0.1 to 0.5 mu m.