Abstract: A high temperature equilibrium experiment was carried out to investigate the effects of temperature on the liquidus lines and equilibrium phase relations of the CaO-Al2O3-FeOx and the SiO2-Al2O3-FeOx ternaries at intermediate oxygen partial pressure of 10.13 Pa. The results of electron probe microanalysis (EPMA) and scanning electron microscope (SEM) showed that the liquidus region of CaO-Al2O3-FeOx system extended to the high Al2O3 region with the temperature increasing from 1450 to 1550°C, and the equilibrated coexisting phases with two-phase and three-phase coexistence were found in the high Al2O3-containing region for the two temperatures. While for the SiO2-Al2O3-FeOx system, the liquidus area expanded to the high iron oxide as well as to the primary region of mullite with the temperature increasing, and the equilibrium phase relations at 1450°C were different from those at 1550°C. In addition, the present experimental results agree well with the FactSage predictions.