Mn3O4 was prepared with the chemical bath deposition (CBD) method. A MnSO4 solution was obtained by the leaching and purifying of low-grade rhodochrosite ore (LGRO), which was used as raw material. The preparation procedures were studied and promoted. The results showed that the Mn3O4 with the highest purity and highest specific surface area could be obtained under the following processes. An MnSO4 solution of 1.0 mol/L was added into a beaker under a flow rate of 30 mL/h. The pH of the reaction solution was adjusted to 10 using NH3·H2O at 80 °C. Then the solids were washed and dried at 200 °C for 2.5 h. The total Mn content (TMC) of Mn3O4 was 72.0 %. The ionic distributions was formulated as [Mn2+][Mn 0.3024 2+ Mn 0.2937 3+ Mn 0.3786 4+ □0.0254]2O4. The average crystallite size of Mn3O4 with a tetragonal hausmannite structure was found to be about 35 nm by X-ray diffraction (XRD) analysis. The BET specific surface area of the Mn3O4 measured was 32 m2/g.