The invention discloses a paper composite electrode and a preparation method thereof. The method includes: taking papermaking paper pulp as the matrix, mixing the matrix with a carbon nanomaterial anda lithium ion battery active electrode material by a mechanical process, and using the mixed slurry to make paper; and rolling the obtained paper into an electrode piece. The preparation method of the paper composite electrode provided by the invention employs easily available and cheap raw materials, has a simple preparation process, can greatly lower the production cost of a flexible two-dimensional electrode, and is conducive to enlarged production. The paper composite electrode obtained by the preparation method provided by the invention has a ternary intertwined structure, integrates theflexible porous structure of wood fiber, the conductive network framework of a conductive carbon material and the lithium ion battery active electrode material, and has excellent charge-discharge specific capacity and cycle stability, flexible two-dimensional shape and high plasticity.