Abstract: Decomposition voltage is an important basis in the exploration of electrode process and in the potential control of actual electrolysis process.The theoretical decomposition voltages of CeO2 and solvents in CeF3-LiF-MF2 （M=Ba，Ca） molten system on the graphite anode were calculated.On the graphite anode，the theoretical decomposition voltage of anode generating carbon oxides was lower and the reaction took place easily；On the inert anode，the theoretical decomposition voltages increased sequentially，in the order of cerium oxide，cerium fluoride，lithium fluoride，barium fluoride，and calcium fluoride and decomposition reaction of cerium oxide will happen firstly.The decomposition voltages of CeO2 and solvents decreased with increment of the temperature and the concentration of CeO2 in the melt，and the anode effect will occur easily when the concentration of CeO2 was too low.

Key words: molten salts electrolysis, fluoride, CeO2, Theoretical decomposition voltage, anode effect