The invention discloses a method for preparing a manganese sulfate solution through manganese oxidized ore thermal-storage reducing roasting. Preparation is performed according to the following stepsthat (1) manganese oxidized ore is crushed, biomass powder is added, mixing and uniform stirring are performed, then a mixture is spread into a roasting box with ventilation holes in the bottom, the material layer is combusted from the surface layer to the bottom layer under the negative micro-pressure air draft, the combustion layer moves to the bottom of the material layer, and then the roastingprocess is finished, so that thermal reducing-roasted ore is obtained; and (2) water, dilute sulphuric acid or electrolytic manganese anolyte are added into a leaching barrel, the thermal reducing-roasted ore is added into the barrel, stirring is performed so that pulp liquid is prepared, then sulfuric acid is added into the pulp liquid, stirring and reaction are performed, then hydrogen peroxideis added, stirring and reaction continue, then a manganese sulfate acid leaching solution is obtained, the acid leaching solution is subjected to neutralization, iron removal and purification, and then the manganese sulfate solution is obtained. The method has the characteristics that the source of reducing agents is wide, the price of the reducing agents is low, the reducing speed is high, the equipment investment is low, energy consumption is low, the manganese reducing leaching rate is high, and the scale is flexible, and the defects in the prior art can be overcome.