The invention provides a lithium-rich pole piece of a lithium ion battery and a preparation method thereof. The lithium-rich pole piece comprises a current collector, a diaphragm and a porous lithium piece, wherein the diaphragm contains an active material and is formed on the current collector; the diaphragm and the current collector form an initial pole piece; and the porous lithium piece covers the diaphragm, and the capacity of the porous lithium piece is matched with the capacity of lithium added to the anode. The preparation method comprises the following steps of: preparing a slurry from the active material, a conductive agent, an adhesive and a solvent, and then applying the slurry on the current collector and drying to obtain the initial pole piece, so that the slurry applied on the current collector becomes the diaphragm after being dried; punching a metal lithium piece to obtain the porous lithium piece, so that the capacity of the porous lithium piece is matched with the capacity of lithium added to the anode; and covering the diaphragm surface of the initial pole piece with the porous lithium piece, to obtain the lithium-rich pole piece of the lithium ion battery. According to the invention, the lithium amount added to the anode can be precisely controlled, the lithium adding uniformity is increased, the first coulombic efficiency, the energy density and the electrochemical properties of the battery are increased, battery deformation is alleviated, the process is simple, and the cost is low.