Abstract: The kinetic data related respectively to S₂O₈^2- formation and O₂ evolution on PbO₂ anode in H₂SO₄ and H₂SO₄-(NH₄)₂SO₄ solutions were obtained by methoed of resolving the steady state polarization curve. The Tafel slopes for both S₂O₈^2- formation and O₂ evolution were 2.303 RT/βF (β=0.52-0.55) at potential higher than + 2.25V vs SHE. The current efficiency of S₂O₈^2- formation was lower than 29% and it almost remained unchanged with potentials. The reaction order of S₂O₈^2- formation with respect to sulfate ions was found to be zero, while the O₂ evolution rate was found to deerease slightly with the increase of sulfate concentration at high potential. A mechanism for above two processes was proposed.