In order to explore the differences in the phase conversion of magnetized roasting iron of self-fusing oolitic hematite at different temperatures, CO gas-based magnetization roasting and magnetic separation experiments are carried out on the self-fusing oolitic hematite. The results show that, in the self-fusing oolitic hematite magnetization roasting process, increasing the roasting temperature can reduce the optimal roasting time and improve the sorting efficiency, while increasing the roasting temperature can increase the iron grade of the magnetic separation concentrate of the roasted ore, but reduce the iron recovery rate of the magnetic separation concentrate. Phase analysis show that the phase variation of magnetized roasting iron of self-fusing oolitic hematite at 800°C is as follows: hematite → magnetite → wustite → iozite; Phase variation of magnetized roasting iron of self-fusing oolitic hematite at 650°C is as follows: hematite → magnetite → wustite. When the self-fusing oolitic hematite gas-based is magnetized and roasted for a long time, the iron in the magnetic separation concentrate of the roasting ore is mainly deposited in magnetite and iozite.