Abstract: Mn²⁺ poisoned Ti/IrO₂-Ta₂O₅-SnO₂ anodes were prepared and the cause of poison was studied by means of current efficiency test, cyclic voltammetry (CV) and SEM. Reactivation of poisoned anodes was also studied. The results showed that the anodes would be Mn²⁺ poisoned when the potentials of anodes reached 1.1 V (v. s. SCE) and Mn²⁺ was oxidized into MnO₂ which would deposit on the surface of the anodes. Galvanostatic reverse electrolysis could reactivate the anodes efficiently, and its best current density was 0. 10 mA/cm².