Abstract: The theoretical specific capacity of polyvalent copper-based oxides is considerable, but their conductivity and stability are inadequate. Graphite phase carbon nitride (g-C₃N₄) exhibits good stability, high nitrogen content and simple synthesis method; however, its capacitance performance is poor. Biochar possesses a substantial specific surface area, relatively good electrical conductivity and rigid structure. To fully leverage the advantages of single phase and compensate for their respective shortcomings, a two-phase compound g-C₃N₄/C with porous structure was synthesized. Urea was served as the precursor of g-C₃N₄, and pleurorus eryngii was selected as the template. Subsequently, CuO was uniformly anchored on the surface and pores of g-C₃N₄/C through hydrothermal method, resulting in three-phase CuO-g-C₃N₄/C. Electrochemical testing reveals that the maximum specific capacitance of CuO-g-C₃N₄/C reaches 262.8F/g, with a capacitance retention rate of 97% after 2000 constant current charge-discharge cycles. CuO-g-C₃N₄/C consistently exhibits excellent charge and discharge performance across different current densities, showcasing superior capacitance and stability of CuO-g-C₃N₄/C. This highlights that the combination of CuO and g-C₃N₄/C in a three-phase structure not only enhances the conductivity of CuO, but also enhances the capacitive performance of g-C₃N₄, thereby improving the energy storage performance, electrical conductivity and stability of the overall material.