An effect of addition of 2 mass % aluminum powder on the oxidation rate of magnesia-carbon refractory, MgO-C, containing 5 mass % carbon has been investigated by measuring weight change with a thermobalance for the cubic specimens in the temperature range from 1073 to 1823 K in air. The oxidation rate of carbon was measured by analyzing the residual carbon in the specimens at some oxidation time. The variations of the weight with oxidation time at temperatures from 1273 to 1673 K showed the similar tendency. The oxidation rate of carbon in the MgO-C refractory with 2 mass % of aluminum additive was a little smaller than that of the MgO-C refractory with no additives. When the oxidation temperature increased to 1823 K, the weight change became very small. It was suggested that the gaps between MgO grains in the thin oxidation layer were bridged by MgO·Al2O3, which was identified by a X-ray diffraction method.