The anodic over-voltage of the carbon anode in aluminum electrolysis is of the order of 0.6V at normal current densities. However, it can be reduced somewhat by doping the anode carbon with various inorganic compounds. A new apparatus was designed to improve the precision of overvoltage measurements. Anodes were doped with MgAI2O4 and AIF3 both by impregnation of the coke and by adding powder, and the measured overvoltage was compared with that of undoped samples. For prebake type anodes baked at around 1150℃, the anodic overvoltage was reduced by 40-60mV, and for Soderbery tpye anodes, baked at 950℃, by 60-80mV