Aluminum nitride (AlN) powder was synthesized by gas reduction–nitridation of γ-Al2O3, using NH3 as the reactant gas. The results showed that AlN can be fabricated by this process at 1100°C for over 480 min in the flowing NH3 atmosphere. However, no AlN was found in the products synthesized at 1300°C and 1400°C, which was different from the former reports. A series of experiments with different parameters were carried out, and the effects of reacting temperature and time on the synthesis of AlN were investigated. The reaction mechanism was also studied.