Developing high-performance electrodes derived from cellulosic wastes is an effective strategy for promoting large-scale energy storage and achieving carbon neutrality, yet how to enhance capacitive activity from the perspective of surface-interface structure regulation remains a challenge. Herein, a disulfide bond reinforced self-assembly of cellulosic wastes strategy is demostrated to fabricate 3D carbon foams with thiram and bio-straws as examples. The cellulose-enriched piths of straws (EP) are impregnated with thiram solution followed by pyrolysis, where thiram can form a stable 3D cross-linked networks via disulfide-centered hydrogen bonds reinforced self-assembly of EP and thiram, endowing the obtained starfish-like skeleton connected 3D carbon foams with high N/S contents and hierarchical porous structure. Consequently, The resultant EPCF-800 as a binder-free and conductive agent-free electrode achieves an ultrahigh specific capacitance of 342 F g