We determined the emissivity of molten oxides using a commercially available pyrometer combined and an electromagnetic levitation system based on the liquid Fe emissivity and its melting temperature. Our method for determining molten oxide emissivity is based on immiscible molten oxides and liquid Fe. From the processes, we obtained 0.80 +/- 0.03 for molten Al2O3 and 0.76 +/- 0.01 for our de-sired molten oxide of SiO2-CaO-Mn3O4-TiO2 system with welding flux model compositions of SiO2:CaO:Mn3O4:TiO2=27:7:13:53 mass%. This is necessary when using ELF (electrostatic levitation furnace) in the ISS (International Space Station) to measure the thermophysical prop-erties of molten oxides. We could correct the monitored with emissivity set at 1 to the real temperature during density measurement by ELF in ISS using normal spectral emissivity for molten SiO2-CaO-Mn3O4-TiO2 system and we find the temperature dependence of molten oxides den-sity of SiO2:CaO:Mn3O4:TiO2=27:7:13:53 mass% in the temperature range of 1200 K -2000 K. We also find that the multicomponent oxide system of SiO2-CaO-Mn3O4-TiO2 has a low coefficient of density temperature dependence.