Lithium-rich manganese-based cathode materials are known as one of the most promising cathode materials for next-generation lithium batteries due to their high theoretical specific capacity. However, there are problems in the cycle process, such as low specific capacity, poor magnification performance, and fast decay rate. Based on this, polymorphic MnO2 materials were prepared by hydrothermal method, and the lithium-rich manganese-based cathode materials were modified of surface coating by wet chemical grinding combined and heat treatment. Electrochemical performance of the obtained materials was tested by cyclic voltammetry, constant current charge and discharge and electrochemical impedance spectroscopy, and the effect of polymorphic MnO2 on electrochemical performance of lithium-rich manganese-based cathode materials was studied by the changes of electrochemical performances of the materials before and after coating. The results show that β-coated has the best electrochemical performance, and its initial specific capacity reaches 292.2 mAh·g-1 at 0.1 C, the capacity retention rate is 56.3% at 0.1~5.0 C, and the capacity retention rate is 81.6% at 1 C for 50 times cycles. The coating of β-MnO2 by EIS test improves electrochemical kinetics of original sample during the electrochemical reaction.