The heterogeneous oxidation of ammonium sulfite solution was investigated in stirred cell and packing column. The concentration range of sulfite is 0.05-4.7 gmol/l and that of oxygen in the gas phase is 21-100%, temperature range is 30-75 degreesC. The results indicated that there is a critical sulfite concentration, below which the reaction order with respect to sulfite is 0.2, while above which the order turns to - 1.0. The reaction order with respect to oxygen is 1. Apparently, the ionic strength was found to inhibit the oxidation. The apparent energy of activation determined is 32.7 kJ/mol.