The induration process of oxidized pellet, containing the oxidation of magnetite phase (Fe₃O₄) and the sintering of oxidized magnetite phase (hematite–Fe₂O₃), is significant to obtain sufficient pellet strength. The current study focuses on the induration mechanisms of MgO flux pellet in terms of the oxidation process of Fe₃O₄ and densification process of the pellet. It is found that MgO dosage negatively affects the oxidation of Fe₃O₄ into Fe₂O₃. The number of recrystallized grain of Fe₂O₃ in the MgO flux pellet is less than that in the Non-MgO flux pellet. Additionally, an unreacted core model was applied to consider and clarify the oxidation of Fe₃O₄. According to the verification experiments, the experimental data and calculated results fit well. Therefore, the unreacted core model can describe the oxidation of Fe₃O₄ in the pellet induration process. Moreover, based on the development of pore parameters during the pellet induration process, a new index, the so-called oxide densification index (ODI) was defined to profoundly specify the densification degree of the pellet. The results show that the ODI of the MgO flux pellet maintains at a lower level compared with that of the Non-MgO flux pellet. It illustrates that MgO can substantially restrain the pellet densification process.