Catalytic oxidation of magnesium sulfite (MgSO3) into magnesium sulfate (MgSO4) is essential for recycling and utilization in the magnesium desulfurization processes. In this paper, laboratory-scale experiments were carried out to compare catalytic activity of different catalysts, which showed that cobalt ions (Co2+) were highly efficient for MgSO3 oxidation catalysis. Moreover, Pilot-scale tests were conducted to validate the major reaction conditions influencing catalytic performance of Co2+, such as air flow rate, pH, temperature, and Co2+ concentrations. Possible reaction mechanism and reaction kinetics of MgSO3 oxidation catalysis was discussed and interpreted, respectively. The MgSO3 oxidation by catalysis has much potential application in the industrial field of the magnesium desulfurization. (C) 2015 Elsevier B.V. All rights reserved.