Carbon-coated LiMnPO4 is prepared by PVP (polyvinyl pyrrolidone)-assisted solid-state reaction. The structure and morphology of the materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical properties of the materials are investigated by galvanostatic charge–discharge test. It is found that the introduction of grinding aid (PVP) in the precursor caused uniform and smaller particle size in the final products, resulting in a regular carbon coating layer around the LiMnPO4 particles. As a result, an improved electrochemical performance is obtained. The carbon-coated LiMnPO4 exhibits a high capacity, a good cyclability and an excellent rate capability. These excellent results are elucidated by electrochemical impedance spectroscopy test, which show that there is decrease of charge transfer resistance and faster Li-ion diffusion in carbon-LiMnPO4 cathode materials after adding PVP.