The interaction between iron oxides and ascorbic acid (AA) normally leads to the degradation of organic pollutants by inducing the generation of hydroxyl radical (OH). However, the influence of different iron oxides on such processes is poorly understood. Moreover, a more complex but very common scenario in real environment is the coexistence of iron oxides with other reactive minerals (e.g., MnO₂), while the underlying mechanism of the interplay of different reactive minerals is still unclear, and knowledge of how the participation of MnO₂ impacts OH generation and pollutant transformation in iron oxides/AA system is an unsolved problem. This study quantified the yields of OH in three iron oxide/AA systems and the transformation of bisphenol A (BPA). We found that AA greatly promoted electron-transfer and OH production on iron oxides, and the OH concentrations were 0.42 mM, 0.24 mM, and 0.08 mM in FeOOH, Fe₂O₃, and Fe₃O₄ systems, respectively. In addition, coexistence of β-MnO₂ inhibited BPA transformation by decreasing OH concentration to 0.19 mM in FeOOH/AA system. This is because β-MnO₂ strongly competed for AA species against FeOOH. In β-MnO₂ system the generated H₂O₂ was very limited in spite of the greater reaction rate, and consequently almost no OH was detected. Interestingly, AA enhanced O₂⁻ production while interacting with MnO₂. Accordingly, the reaction mechanism for the interaction between β-MnO₂ and AA involving reactive oxygen species (ROS) generation was achieved at the molecular level. This study elucidates the effect of environmental factors on the ROS formation by Fe/Mn oxides, and provides a theoretical basis for understanding realistic environmental processes.