The present invention discloses a method for preparing lithium-rich manganese-based cathode material. The method comprises: dispersing α-MnO2 micron particles, a nickel salt and a lithium-containing compound in a solvent to obtain a mixture, then evaporating the mixture to remove the solvent, and calcining the solid product obtained from the evaporation; wherein the lithium-containing compound is a lithium salt and/or lithium hydroxide. The present invention also provides a lithium-rich manganese-based cathode material prepared by the above method. The present invention also provides a lithium-ion battery of which anode material contains the foregoing lithium-rich manganese-based anode material. The lithium-rich manganese-based cathode material provided by the present invention has high rate capability and prolonged cycle stability.