The application of carboxylic acid and natural iron oxide in heterogeneous AOP systems for the treatment of organic pollutants in water has attracted extensive attention. In this work, ethylenediamine-N,N′-disuccinic acid (EDDS) was complexed with ferrihydrite to improve the photo-Fenton system for bisphenol A (BPA) degradation, and the mechanism of the system was investigated. TEM, XRD and BET were used to investigate the morphology, structure and specific surface area of ferrihydrite. The characterization results revealed that ferrihydrite was amorphous and agglomerated, its main composition was 2–2lfh, and its specific surface area was 297.5 m2 g−1. BPA degradation experiments, carried out at different influence factors including the initial concentration of EDDS, amount of ferrihydrite and initial concentration of H2O2, showed a maximum degradation rate of BPA of 85.1% under the optimal conditions (at 1.0 mmol L−1 EDDS, 0.6 g L−1 ferrihydrite and 0.5 mmol L−1 H2O2). Finally, in order to analyze the mechanism of BPA degradation, 2-propanol and chloroform were used as free radical scavengers to capture hydroxyl radicals (˙OH) and superoxide anion radicals (˙O2−) respectively. The results indicated that ˙OH radicals and 1O2 play an important role under aerobic conditions, while ˙O2− radicals produced by the reaction of H2O2 and holes are non-negligible under anaerobic conditions. Moreover, the iron dissolution also plays a promoting role in BPA degradation. Overall, Fe(III) and Fe(II) redox processes are accelerated due to the Fe(III)–EDDS complex reaction under irradiation and in the presence of ˙O2− radicals and trace iron dissolution, which increases the number of reactive species in the system. The BPA degradation is facilitated by various reactive species including ˙OH radicals, 1O2 and ˙O2− radicals.