it is well know that CaTiO₃ is the evitable interphase produced during electrolysis of TiO₂ in molten CaCl₂. Here, the relationship between formation of CaTiO₃ and deoxygenation of TiO₂ and emition of gas on the anode is studied by the intermittent experiments. The results show that the process of deoxygenation from TiO₂ to Ti can be dividied three stages. The first stage is deoxygenantion of TiO₂ and formation of CaTiO₃. The second is deoxyenation and decalcification of CaTiO₃ to Ti₂O including deoxygenation of titanium suboxides. The final stage is deoxygenation from Ti₂O to Ti (2% O). the mole ratio of O_2- and Ca₂₊ and CaTiO₃ is 1:1:1. Cl₂ releases from the anode when CaTiO₃ is formed in the cathode. If the whole electrolysis time from TiO₂ to Ti (2% O) is thought 100%, the cost time of stage I, stage II and stage III is 5.6%,38.9%, 55.5% respectively. Formation of CaTiO₃ and deoxygenation of Ti₂O to Ti are both main factors of the low current effeciency.