The processes of the formation and reduction of the basic lead sulfates (3PbO.PbSO4.H2O and PbO.PbSO4) have been studied by electrochemical techniques. Experiments indicate that 3PbO.PbSO4.H2O is mainly formed at -200 mV while the amount of PbO.PbSO4 formed is very small. The peak potential for the reduction of 3PbO.PbSO4.H2O becomes more negative with the increase of the sweep rate and the amount of 3PbO.PbSO4.H2O. Besides the PbSO4 passivation film, basic lead sulfate layers can seriously obstruct the anodic film from growing. Both the formation and reduction of the basic lead sulfates occur via a dissolution-deposition mechanism. During oxidation, the SO42- ion is produced through the dissolution of PbSO4. During reduction, the SO42- ion reacts with the Pb2+ ion to form PbSO4 again; the diffusion of the OH- from the inner layer to the bulk solution is the rate-controlling step.