The effects of magnetic field intensity, roasting temperature and roasting time on digestion rate and settling performance of bauxite with different iron contents were investigated systematically. The results indicate that such magnetic treatment can profoundly change the microstructure and digestion performance of bauxite. For the two samples carrying different iron contents, phase transformation of the aluminum oxide phase proceeds faster in the high iron bauxite than the low one. The optimal pretreatment conditions of low iron bauxite are roasting temperature 550 °C and magnetic field intensity 6 T, while for high iron bauxite are 500 °C and 9 T. The digestion rate of alumina can reach 95% and 92% at digestion temperature of 190 °C and 250 °C. The settling performances of roasted ore by intense magnetic field after digestion are enhanced through pretreatment.