In this paper, a series of aluminum nitride powders were synthesized using a microwave synthesis method with various additives. The effects of additives on the nitridation of aluminum powder by microwave processing were studied. The results showed that the pure AlN powder with regular and fine grains could be obtained at a temperature of 1050 degrees C for 30 min by the mixed additive under atmospheric pressure of nitrogen. The mixed additive composed by ammonium fluoride and zinc granules played a vital role in the microwave synthesis process.