The invention relates to a method for preparing a lithium manganate anode material by electrolytic manganese. The method comprises the following steps: (1) carrying out acid leaching on electrolytic manganese slags, and extracting manganese dioxide as a manganese source; (2) mixing the manganese source with a lithium source, and carrying out high-temperature solid phase method reaction to prepare the lithium manganate anode material. The invention provides a novel and new way of processing the electrolytic manganese slags, waste can be changed into valuable matters, the problem that the electrolytic manganese slags pollute the environment is solved, the utilization ratio of the electrolytic manganese slags is increased and the additional value of the electrolytic manganese slags is improved.