Abstract: In this work, microwave energy was used for roasting treatment of diaspora bauxite mixed with saturated NaOH solution as an additive. The influences of microwave heating temperature and NaOH addition on the phase transformation of the diaspora ore-sodium hydroxide system were investigated. The phase constitution of the roasted ore in microwave heating and conventional heating processes was compared under the same experimental conditions. The phase composition and microstructure of the roasted ore were comparatively analyzed by X-ray diffi'action analysis and scanning electron microscopy. The results show that microwave roasting can facilitate the rapid and complete reaction between NaOH and the diaspore ore, leading to more NaAI02 phase forming at lower temperature as compared to conventional heating. After microwave heating, the roasted ore is porous, good for subsequent digestion processes.