The iron phthalocyanine (FePc) monolayer adsorbed on a graphite surface showed a remarkable activity for the SO2 reduction in aqueous conditions. The highest activity was observed at strongly acidic solutions and decreased with a pH increase due to the H+ limitation of reduction. Only SO2 and HSO3- are reducible forms. The reduction mechanisms at strongly and moderately acidic conditions were suggested. The SO2 reduction current was independent of the surface coverage and the ppb level detection was possible with amperometry.