Abstract: The mechanism of the cathode process of B(Ⅲ) on a platinum electrode in molten LiF-NaF-KBF₄ at 750℃ has been investigated by means of cyclic voltammetry and convolution technique.It Was found that the electrochemical reduction of B(Ⅲ) to elementary boron is a simple three-electron process involving alloy formation with the platinum electrode.The cathodic process is very close to a reversible process and is diffusion controlled.