Recycling of iron oxide from BOF slagshas always been a difficult issue in metallurgy. The core of this study was transforming the iron oxide into ferromagnetic phase MgFe₂O₄ by modifying industrial BOF slag appropriately first, and then recycling the iron resources by magnetic separation. The effect of basicity and calcination temperature on the formation of MgFe₂O₄ in synthetic BOF slags was investigated first, and then the industrial BOF slag was modified. Various experiments and analyses such as XRD, SEM-EDS, Factsage thermodynamic simulation and chemical analyses were conducted.The results show that the optimal basicity was 2, and the optimal calcination temperatures were 1 250 and 1 300℃. Moreover, MgFe₂O₄ was formed in modified BOF slag by mixing the industrial BOF slag with 6% SiO₂ first, and then cooling the modified BOF slag from 1 400 to 1 270℃ at a rate of 1℃/min. After magnetic separation, the total Fe content in magnetic slag increased by 15.80%, to 37.00%, compared with that in the industrial BOF slag. This is better than the direct magnetic separation of iron oxide without any treatment