The invention provides a layered structure nanometer lithium manganate-inlaid graphene-coated positive electrode material for a lithium-ion battery, an electrode and a preparation method, relates to the field of secondary batteries, in particular to a surface-coated modified positive electrode material for the lithium-ion battery, the electrode and the preparation method of the positive electrode material, and aims at solving the problems that the positive electrode material for the lithium-ion battery is low in capacity and poor in rate capability since an existing coating material is relatively poor in electron conductivity and ion conductivity. According to the positive electrode material provided by the invention, the layered structure nanometer lithium manganate-inlaid graphene-coated positive electrode material with a lithium ion diffusion channel and a nanometer size for the lithium-ion battery and the electrode of the battery are prepared by an electrochemical reduction method. Graphene of a coating layer has high electron conductivity; the layered structure lithium manganate with the nanometer size inlaid on a graphene sheet layer has the lithium-ion conductivity; and the positive electrode material, a conductive agent and a binder are mixed and coat a current collector to form the electrode. The positive electrode material and the electrode provided by the invention are applied to the lithium-ion battery.