Abstract: The apparent conductivities of the slag CaO-SiO2-MgO-Al2O3-TiO2 containing TiC particles of different sizes and concentrations were measured by A.C. impedance spectrum technique at 1633 K. An equivalent circuit was proposed rationally to simulate the A.C. impedance spectra of the slag, and the apparent activation energies of the slag were estimated from the relationships between the apparent conductivities and the temperature at the range of 1633-1693 K. The results indicated that the apparent activation energy of the slag would increase with increasing content of TiC particles and decreasing particle size. When the mass fraction of TiC is 0.5%, the apparent activation energy would decrease slightly with decreasing TiC particle size. The apparent conductivity of the slag would decrease with increasing TiC content and decreasing TiC particle size at 1633 K. When the mass fraction of TiC is 0.5%, the apparent conductivity of the slag would increase slightly with TiC particle size. In sum, the relationship between the apparent conductivity and temperature of the slags of the same TiC content and particle size at the temperature range 1633-1693 K is in conformity with Arrhenius relationship.