Abstract:The lime digestion process of low grade bauxite with diaspore as the main mineral was studied. Digestion scheme and optimization technical parameters were determined. The process parameters effected the digesting rates of bauxite, such as caustic concentration, temperature, liquid-solid ratio, lime addition and time, were investigated. The experimental results show that 90.03% Al₂O₃ is digested from bauxite in the following conditions: the caustic concentration 240g.L_-1, the temperature 270℃, the liquid-solid ratio 6:1, the lime addition 8% of the mass of the ores, the time 60 min. The addition of lime can not only decrease the digestion of SiO₂, but also increase Al₂O₃ digesting rate observably.