The equilibrium constant, K c , of the reaction 3Ti 2+ = 2Ti 3+ + Ti was studied in the molten binary mixtures of LiCl. The accurate values of K c were calculated by the best-fitting method under consideration of the TiOCl(s) dissolution at temperature of 973 K, 1023 K and 1073 K, respectively. The fitted concentration of O 2− was verified by emf method with yttria-stabilized zirconia electrode (YSZE). The influence of the cation radius of electrolyte on the equilibrium constant was studied in molten binary mixtures of LiCl at 1023 K on the basis of the reliable method for obtaining accurate value of K c . It was found that the K c values decreased from 0.59 to 0.27 with the concentration of LiCl increasing at 1023 K. More importantly, results disclosed that the values of K c correspond with polarizing power no matter in CsCl-LiCl or KCl-LiCl system.