Abstract: Supercapacitors, as emerging energy storage devices, have demonstrated promising application prospects in the field of energy storage owing to their considerable specific capacitance, high power density, rapid charge/discharge capability, excellent safety performance, and environmental friendliness. Their performance primarily depends on the structural and chemical properties of the electrode materials. Among various candidate materials, graphitic carbon nitride (g-C₃N₄), as a two-dimensional carbon material, has great potential as an electrode material for double-layer capacitors due to its abundant nitrogen doping, high-density active sites, and excellent morphological stability. This paper systematically reviews the electric double layer-pseudocapacitive synergistic energy storage mechanism of g-C₃N₄ and provides a comprehensive analysis of synthesis strategies, structure-property relationships, and performance optimization pathways for various g-C₃N₄-based composite electrode materials (such as those combined with metal compounds and conductive polymers) from the perspective of synergistic integration of microstructural regulation and interfacial engineering. However, the practical implementation of g-C₃N₄-based composites still faces challenges such as low intrinsic electrical conductivity, unclear synergistic energy storage mechanisms, and insufficient electrode structural stability. Future efforts should focus on developing multidimensional heterostructures, advancing multicomponent hybridization with emerging materials like MXenes and MOFs, and integrating in situ characterization with theoretical calculations. Through dynamic interfacial engineering designs enabling precise regulation of components and structures, these strategies will overcome current performance bottlenecks and promote practical applications in energy storage and conversion fields.