Abstract: With the growing global demand for efficient energy storage technologies, supercapacitors have become a research focus due to their high power density, long cycle life, and fast charge-discharge capabilities. This study presents a novel nitrogen-sulfur co-doped three-dimensional graphene-supported copper-based metal-organic framework (NS-3DPG-CuBTC) composite material as an electrode material for supercapacitors. Using an improved hydrothermal synthesis method, nitrogen and sulfur heteroatoms were co-doped into the three-dimensional graphene structure, which was then successfully combined with the copper-based metal-organic framework CuBTC to form a composite material with high porosity and abundant active sites. The material’s structure and morphology were systematically characterized using techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analysis, and Fourier-transform infrared spectroscopy (FTIR). Electrochemical testing results show that the NS-3DPG-CuBTC electrode exhibits excellent specific capacitance, reaching up to 755.43 F·g⁻¹ in a 3M KOH electrolyte, while maintaining good capacitance performance at different scan rates and current densities. The assembled symmetric supercapacitor demonstrates high energy density (27.96 Wh·kg⁻¹) and power density (1473.73 W·kg⁻¹) within a voltage window of 0–0.8 V, and after 2000 charge-discharge cycles, the capacity retention reaches 94.06%, indicating excellent cycle stability. The experimental results indicate that the nitrogen-sulfur co-doping strategy effectively improves the electrochemical performance of the material, enhancing the electrode’s conductivity and ion transport efficiency, while maintaining good long-term stability.