Due to the importance of the physicochemical properties of slag in the recovery of low-titanium ores and by-products, the equilibrium phase relationships of the CaO-MgO-Al 2O 3-SiO 2-TiO 2 system were experimentally determined using a high-temperature equilibration and quenching method at 1300°C and 1400°C. The equilibrium information was obtained by scanning electron microscope–energy dispersive x-ray spectrometer. Perovskite, spinel and pseudobrookite solid solution phases with MgO·2TiO 2 and Al 2O 3·TiO 2 end members were found to be coexisting with the liquid phase. The 1300°C and 1400°C isotherms were then constructed on a CaO-SiO 2-TiO 2-8 wt.% MgO-14 wt.% Al 2O 3 quasi-ternary section. Comparisons with predictions by Factsage and MTDATA indicated that the computational results agreed well only in the primary phase field of perovskite, while clear deviations existed within other primary phase fields. Therefore, the present results improve our knowledge about the utilization of titanium resources, and are also significant in providing novel equilibrium data for updating the related thermodynamic databases.