The single-phase AlON powder used to prepare transparent ceramics was synthesized from solid-state-reaction using nano-sized Al2O3 and AlN powders with high purity. An appropriate amount of the powder was molded into pellets and isostatically pressed using polyvinyl alcohol as the binder. The AlON ceramic samples were obtained by sintering the pellets at 1880°C for 10 h, 20 h and 40 h, respectively. The transparency of the samples increased as the temperature holding time was prolonged. The density, phase compositions and microstructures of the sintered samples were discussed in detail.