Abstract: By externally adding Fe(Ⅱ) and Fe(Ⅲ) to the reaction system, this study focuses on investigating the production of reactive oxygen species (ROS) mediated by the surface of goethite and its enhancement mechanism for the oxidation and transformation of As(Ⅲ). The analyses with XRD, ESR, and XPS indicated that ROS generated in the oxidation of the ferrihydrite/Fe(Ⅱ) system under weakly acidic pH conditions includes hydroxyl radical ·OH, singlet oxygen ¹O₂, and superoxide radical ·O₂^-, while the Fenton like reaction for the ·OH production is a single electron transfer process. Approximately 364.82 μmol/L H₂O₂ can be generated during the oxidation reaction of ferrihydrite/Fe(Ⅱ) system for 120 min, and the presence of O₂ highly determined the generation of H₂O₂. The ·OH cumulative concentration in the above ferrihydrite/Fe(Ⅱ) system is positively correlated with the amount of Fe(Ⅱ) to be oxidized. A weak weak acidic condition at pH 6 is more favorable for the ferrous oxygenation reaction system to produce ·OH, wherein the ·OH cumulative concentration is about 30.69 μmol/L. Moreover, the oxidation of As(Ⅲ) by ROS such as ·OH species mainly occurs on mineral surfaces. The presence of Fe(Ⅱ) is conducive to the occurrence of As(Ⅲ) oxidation to form As(V) in the system, but due to competitive adsorption, the Fe(Ⅱ) adsorption may not be conducive to both the adsorption of As(Ⅲ) and its subsequent interfacial oxidation in the system. As a result, this study will contribute to well-understanding of the synergistic mechanism of Fe(Ⅱ) reactivity mediated by mineral surfaces coupling with the enhancement in arsenic pollution environmental purification, and thus may provide the experimental and theoretical bases for practical arsenic contaminated soil environmental remediation.