The flowerlike micro/nanostructured bismuth oxide is synthesized by the solvothermal reaction using ethylene glycol-ethanol solution of bismuth nitrate pentahydrate. The as-synthesized bismuth oxide powders consist of the flowerlike microscaled particles with the size mostly falling into the range of 2-5μm. The particles are built with the cross-linked nanosheets of 5-10nm in thickness. Such micro/nanostructured bismuth oxide particles are, stoichiometrically, Bi6O7 or Bi2O2.33. Importantly, this material has exhibited the highly efficient adsorption performances to both negatively univalent iodine ions I- and quinquevalent iodine ions I(V) (or IO3-) with fast kinetic processes and high capacities. The maximum adsorption capacities are up to 285 and 229mgg-1 for I- and I(V), respectively, which are much higher than those for the most reported adsorbents. This highly efficient iodine removal performance is attributed to the adsorption-induced chemical reaction mechanism as well as the micro/nanostructure of the flower-like Bi2O2.33 particles. Further experiments have demonstrated that such material has a strong selectivity to both I- and I(V) in the solution with largely excessive competitive anions such as nitrate and sulfate, can work in a wide pH range from 3 to 11, and has exhibited good practicability for highly efficient iodine removal from the real iodine-contaminated waters. This work not only deepens understanding of iodine adsorption behaviors, but also provides a promising iodine adsorbent.