Abstract: The equilibrium phase relations of the CaO–SiO₂–TiO₂–5wt%Fe₃O₄ system were experimentally investigated at 1400°C in air. High-temperature equilibration-quenching techniques were employed in an electric MoSi₂ resistance heated furnace, with phase composition analysis conducted using an electron probe microanalyzer and X-ray diffraction. A single liquid region, liquid–solid phase equilibria regions (including liquid–tridymite, liquid–rutile, liquid–perovskite, and liquid–wollastonite), and three-phase equilibria regions of liquid–tridymite–rutile and liquid–rutile–perovskite were found. The 1400°C isothermal sections of the CaO–SiO₂–TiO₂–5wt%Fe₃O₄ system in air were projected. The present experimental results exhibited good agreement with the calculation results obtained from FactSage.