Aluminum oxycarbides were prepared via a carbothermal reduction of alumina in vacuum at 1 300 - 1 500 ℃. The results indicate that the temperature required for the formation of aluminum oxycarbides from the carbothermal reduction of alumina in vacuum is lower than that in argon, a large amount of Al4O4C can be formed at 1 300 ℃, and the main component of the condensation products is Al4O4C, which is independent of the reaction extent of the raw materials. The condensation products consisting mainly of Al4O4C with a small amount of Al4C3 can be obtained under optimum conditions (i.e., n(α-Al2O3):n(C) of 2:3, reaction temperature of 1 400 ℃ and reaction time of 20 min). It is confirmed that Al4O4C can be formed in two stages, i.e., alumina reacts with carbon to generate the gases containing aluminum Al2O, Al and CO at higher temperatures, and the condensates mainly consisting of Al4O4C form at lower temperatures.