Manganese dithionate is a byproduct, accompanied by the formation of manganese sulfate, of the leaching process of sulfur dioxide (SO2) with pyrolusite. The as-produced MnS2O6 is disadvantageous for recovering MnSO4 by debasing the purity of the MnSO4 product. To obtain the qualified MnSO4 product, removing MnS2O6 from the leaching solution is critical. In this work, the conversion characteristics of MnS2O6 in the H2SO4-MnO2 system were studied. The conversion mechanisms of MnS2O6 were determined by a material balance of sulfur. The effects of the operating parameters, including the concentrations of H2SO4 and MnS2O6 and the temperature, on the conversion rate of MnS2O6 were investigated. The kinetic characteristics of the MnS2O6 conversion were analyzed. The results indicated that MnS2O6 decomposed into MnSO4 and SO2 in the H2SO4-MnO2 system through two pathways. (A) MnS2O6 decomposed into MnSO4 and SO2 in the presence of H2SO4 in the disproportionation reaction, and SO2 was oxidized to MnSO4 by MnO2 in the liquid phase. (B) The direct oxidizing reaction of MnS2O6 with MnO2 resulted in the formation of MnSO4 in H2SO4 solution. The former pathway was predominant in the MnS2O6 conversion. In addition, based on the results of the MnS2O6 conversion in the H2SO4-MnO2 system, the kinetics analysis of the composite reaction was conducted, and the apparent activation energy (Ea) of 204.6 kJ mol(-1) was obtained. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.