Activated carbon (AC) sourced from biomass is commonly utilized in supercapacitor applications, yet its higher cost is often a drawback, primarily due to the low yield associated with its limited carbon content. As an alternative, petroleum coke (PC) emerges as a promising precursor for AC production, owing to its high carbon content of approximately 90 wt%. This research presents a facile, high-yield approach for synthesizing porous, sulfur-doped activated carbon from PC, referred to as S-PAC. Characterized by its amorphous structure and significant porosity, S-PAC boasts a BET surface area of nearly 450 m2/g. S-PAC exhibits outstanding electrochemical performance when integrated into a symmetric supercapacitor, achieving a specific capacitance of approximately 140 F/g at a current density of 0.5 A/g. Moreover, the S-PAC-based supercapacitor demonstrates superior charge-discharge cycle stability, highlighting the material's excellent capacitance efficiency. The effectiveness and simplicity of S-PAC as an electrochemical energy storage material emphasize the importance of this study.