Abstract: Vanadium-titanium magnetite is one of the important raw materials for iron making in a blast furnace. Ca₃TiFe₂O₈, which is a mineral of vanadium-titanium sinter, was discovered to form during the process; however, its formation mechanism is not clear. In this work, an X-ray diffraction analysis, an elemental spectroscopy, and a TG-DSC were employed to investigate the formation mechanism of Ca₃TiFe₂O₈ and the formation law at different temperatures and at CaO and TiO₂ contents in the CaO-TiO₂ -Fe₂O₃ system. The formation mechanism of Ca₃TiFe₂O₈ is clarified:CaO reacts with Fe₂O₃ to form Ca₂ Fe₂O₅, and then continues to react with the CaTiO₃ to form Ca₃TiFe₂O₈. The longer the reaction time, the greater is the amount of Ca₃TiFe₂O₈ formed. However, the effect of temperature on the formation of Ca₃TiFe₂O₈ is not obvious. It is found that high CaO content contributes to the formation of Ca₃TiFe₂O₈. Further, so long as TiO₂ is present, Ca₃TiFe₂O₈ is formed under the condition of equal molar concentration Fe₂O₃ and CaO.