Fused magnesia is prepared by melting selected grade A natural magnesite or high-purity lightly burned magnesium particles in an electric arc furnace. The product has high purity, large crystal grains, compact structure, strong slag resistance and good thermal shock stability. It is an excellent high-temperature electrical insulation material and an important raw material for making high-grade magnesia bricks, magnesia-carbon bricks and unshaped refractories.