Photocatalytic H2O2 synthesis (PHS) via graphite carbon nitride (g-C3N4) is a low-carbon and environmentally friendly approach, which has garnered tremendous attention. However, as for the pristine g-C3N4, the PHS is severely constrained by the slow transfer and rapid recombination of photogenerated carriers. Herein, we introduced cellulose-derived carbon nanofibers (CF) into the homojunction of g-C3N4 nanotubes (MCN) and g-C3N4 nanosheets (SCN). A series of photocatalytic results demonstrate that the embedding of cellulose-derived carbon for MCN/SCN/CF composite catalyst significantly improved the photocatalytic H2O2 generation (136.9 μmol·L−1·h−1) with 5-holds higher than that of individual MCN (27.5 μmol·L−1·h−1) without any sacrificial agent. This enhancement can be attributed to the combined effects of the two-step one-electron oxygen reduction reaction (ORR) on conduction band (CB) side and the water oxidation reaction (WOR) on valence band (VB) side. A comprehensive characterization of the mechanism indicates that CF enhances the absorption of light, promotes the separation and migration of photogenerated carriers, and regulates the position of the valence and conduction bands with an effective dual-channel ORR pathway for photo-synthesis of H2O2. This work provides valuable insights into utilizing biomass-based materials for significantly boosting photocatalytic H2O2 production.