The kinetic processes of both PbSO4 oxidation and the oxygen evolution reactions were studied under pulse charging conditions. Three hinds of diffusion processes appeared in the positive active mass. The time intervals required to relax the respective concentration polarizations were about 0.1, 300. and more than 10000 s. At the beginning of the pulse charge, the passivation layer formed between the grid and active mass at the positive plates exhibited a poor electronic conductivity and impeded the diffusion of O atoms. Thus, the electrode polarization increased and oxygen evolution accelerated. Following the initial pulse, the diffusion of O atoms became rapid while the concentration of ions such as HSO4- and SO42-at the reaction surface increased gradually so that their dif fusion became dominant in the solution near the reaction surface. For longer times, the charge rate was controlled by the diffusion of these ions in the micropores of the active mass. The electrode polarization. oxygen evolution, and loss of water can be inhibited by using a pulse discharge or/and prolonging the off-time of pulse charge.