The method of electro-deoxidation was used to reduce solid TiO2 to titanium in CaCl2 molten salt at 900 ℃. The sintered TiO2 samples acted as the cathode and graphite as the anode. The formation and transportation process of O2- in the electrolytic system with molten salts were studied. Results show that the experiment high-temperature promotes the formation of oxygen vacancies in TiO2 structure and occurrence of O2-; O2- transfer from the cathode inside to outside through the oxygen vacancies; the calcium titanate is necessary intermediate product in the electrolysis process; the dense layer of metal titanium on the cathode surface hinders O2- from transformation.