The invention provides a method for preparing high-purity manganese sulfate through extracting low-grade pyrolusite by using rice straw. The method comprises the steps of adding a sulfuric acid solution and dry rice straw into pyrolusite, reacting at the temperature of 70-950 DEG C for 8-15h while continuously stirring, and filtering to obtain pyrolusite leachate; respectively removing heavy metal ions such as iron ions, Ni<2+> and Co<2+> as well as calcium and magnesium ions by using an ammonia solution, barium sulfide and ammonium fluoride to obtain an initial solution of manganese sulfate; adding ammonium carbonate to form a white sediment, filtering, mixing the obtained solid and 500-DEG C water, stirring for 10 minutes, filtering, mixing the obtained solid and 500-DEG C water, stirring for 10 minutes, and then, filtering to obtain solid manganese carbonate; and adding the sulfuric acid solution to completely dissolve the solid manganese carbonate, continuing to stir for 30 minutes, heating to concentrate the solution, crystallizing, centrifugally dehydrating, and drying in hot air to obtain high-purity solid manganese sulfate. By using the method, the process flow is simplified, the operation condition is improved, the energy consumption is greatly reduced, and the industrial application prospect is huge.