The mullite powders are prepared through solid-state reaction of manufactured alumina and silica fume in air atmosphere. The influences of calcination temperature and different Al₂O₃/SiO₂ ratios of the amount of substance on the crystalline phases are discussed. The results show that the powder has the maximum mullite content of 95% by K calculating when the Al₂O₃/SiO₂ ratio of the amount of substance and the calcination temperature are 3:2.5 and 1450℃, respectively. On this basis, the relationship between the mullite powders property and the milling time is investigated using particle size distribution analyzer, BET tester and field emission scanning electron microscopy. The average size of mullite powders diminishes with the milling time, with the diameter distribution evolving from unimodal distribution to bimodal distribution. The average size of as-prepared mullite powders is 0.58μm and its BET value is 9.26m²/g. The as-received mullite powders present an irregular shape of polygon.