The invention belongs to the field of battery material processing, and specifically relates to a preparation method of manganese sulfate for electrolytic manganese dioxide. The preparation method comprises the steps of manganese sulfate leaching and neutralization for iron removal, impurity removal of heavy metals, electrolysis and post-processing; concretely, manganese oxide ore powder, pyrite powder and an industrial sulphuric acid are subjected to high-temperature and high-pressure leaching in the presence of SO2 so as to prepare a coarse manganese sulfate solution, then the coarse manganese sulfate solution is subjected to iron removal by using calcium carbonate and subjected to primary heavy metal removal by using barium sulphide, and an adsorbent is added to secondarily remove trace elements, so that the concentrations of the trace elements such as As, Sb and Mo are all less than or equal to 0.005 ppm, thereby obtaining a manganese sulfate solution with a good quality. The content of impurities such as Fe, Cu, Pb, Ni, Co, K, Na, Ca, Mg, and the like in the manganese sulfate solution prepared by using the method disclosed by the invention is low, wherein the content of Cu is less than or equal to 2.0 ppm, the content of Pb is less than or equal to 3.0 ppm, the content of Ni is less than or equal to 2.0 ppm, and the content of Co is less than or equal to 2.0 ppm.