Long-term exposure to excessive iodine via drinking water significantly increases the risk of thyroid diseases. Further, the mechanisms and feasible technologies for iodine removal are far from being well elucidated. In this study, we constructed a heterogeneous Bi₂O₃@MnO₂ interface with oxidation and adsorption efficiency toward iodide (I⁻), and investigated the performance and mechanisms involved in iodine removal. Bi₂O₃@MnO₂ at the optimized Bi/Mn ratio of 0.05:1 had a maximum adsorption capacity of 1.19, 1.21, and 1.06 mg/g toward I⁻, iodine elemental (I₂), and iodate (IO₃⁻), respectively. According to the density functional theory (DFT) calculation, Bi₂O₃@MnO₂ had an adsorption energy of -2.34, -2.11, and -3.89 eV for I⁻, I₂, and IO₃⁻, and exhibited a better band structure and state density character for iodine removal. Based on the results of XPS, HPLC, and LC-ICP-MS characterization, Bi₂O₃ plays an important role in adsorbing and capturing I⁻ whereas MnO₂ dominates the moderate oxidation of I⁻ and the adsorption of I⁻ and I₂. The adsorbed I⁻ and I₂ concentrations on the Bi₂O₃@MnO₂ surfaces were 146.3 μg/L and 18.3 μg/L. Notably, IO₃⁻ was not detected owing to its moderate oxidation effect. The coexisting ions of chloride (Cl⁻) and bromide (Br⁻) tended to occupy the Bi₂O₃ lattice and form insoluble BiOCl and BiOBr. Further, reductive species, such as sulphite (SO₃²⁻), may reduce MnO₂ to Mn(III) and Mn(II). The synergistic effect between moderate oxidation and adsorption led to Bi₂O₃@MnO₂ with high iodine removal capability. Overall, this study proposes a strategy for designing suitable interfaces and adsorbents for iodine removal; however, further studies are necessary to advance its application in practice.