CaB6 powder was synthesized by molten salt electrolysis method, and the effects of synthesis temperature, electrolysis voltage and time on the phase composition, particle size and shape of cathode products were analyzed by XRD and SEM. The experimental results show that the best synthesis conditions of CaB6 powder in CaCl2 molten salt system are: environment of argon, voltage of 3.0 V, temperature of 900C for 30 h, under which the range of CaB6 crystal size is 2-8 μm and the morphology of particles is cuboid massive shape. Using cyclic voltammetry in cathode process, it is proved that the electrolysis process is controlled by the diffusion rate of borate to the cathode.