The invention provides a hyperbranched polymer electrode active material and a preparation method. The hyperbranched polymer electrode active material is a pure hyperbranched polymer material or a hyperbranched polymer/carbon composite material. The hyperbranched polymer/carbon composite material is formed by combining the pure hyperbranched polymer with a carbon nanomaterial. The preparation method comprises the following steps of: mixing and reacting poly-isocyanate, a material I, and a solvent to obtain a pure hyperbranched polymer material as the electrode active material; or mixing and reacting the poly-isocyanate, the material I, the carbon nanomaterial, and the solvent to obtain the hyperbranched polymer/carbon composite material as the electrode active material, wherein the material I is any one of polyamine, polyhydric alcohol, and polyhydric alcohol amine. The method prepares the hyperbranched polymer with good electrochemical performance and the composite material thereof, so that the traditional low-added-value hyperbranched polymer can be used as the electrode active material of a lithium or sodium ion battery, thereby reducing the cost of the energy electrode material.