[en] The behaviour of iodine in the dissolution process of nuclear fuel is investigated. Unirradiated UO₂ pellets were used in the study. The test shows that possible I^- or IO₃^- can be reduced or oxidized to elemental iodine by HNO₂ present in HNO₃ and produced in dissolution process of UO₂. The result shows that 87 ∼ 99.4% of ¹³¹I can be removed in the period of 3.5 ∼ 6 hours at 95 deg C and boiling point respectively. The adding of stable isotope of iodine to the dissolver can improve the removal of ¹³¹I. It is difficult to remove iodine from the solution when the concentration of iodine is lowered down to 10^-6 mol/L. The strengthening of sparging-air would favour to removal of iodine from dissolver solution. More than 90% of radioiodine goes to gas-off system by sparging-air in the process of dissolution