Designing polymeric photocatalysts at the molecular level to modulate the photogenerated charge behavior is a promising and challenging strategy for efficient hydrogen peroxide (H2O2) photosynthesis. Here, we introduce electron‐deficient 1,4‐dihydroxyanthraquinone (DHAQ) into the framework of resorcinol‐formaldehyde (RF) resin, which modulates the donor/acceptor ratio from the perspective of molecular design for promoting the charge separation. Interestingly, H2O2 can be produced via oxygen reduction and water oxidation pathways, verified by isotopic labeling and in situ characterization techniques. Density functional theory (DFT) calculations elucidate that DHAQ can reduce the energy barrier for H2O2 production. RF‐DHAQ exhibits excellent overall photosynthesis of H2O2 with a solar‐to‐chemical conversion (SCC) efficiency exceeding 1.2 %. This work opens a new avenue to design polymeric photocatalysts at the molecular level for high‐efficiency artificial photosynthesis.