Abstract: Removal of ¹³¹I is crucial to ensure the quality of medical fission ⁹⁹Mo. The whole radiochemical extraction process of fission ⁹⁹Mo from simulated solution had been developed by -benzoin oxime precipitation, followed by AG1-×8 anion exchange and activated charcoal chromatography for further purification.To evaluate the effectiveness of removal of radioactive iodine by the established production process for fission ⁹⁹Mo, in this work, behavior of ¹³¹I^- and ¹³¹IO^-₃ in the chemical process had been studied. The decontamination effectiveness of ¹³¹I^- and ¹³¹IO^-₃ had been evaluated. For ¹³¹I^-, 98.2% of iodide in the simulated solution could be precipitated by AgNO₃ as AgI sal, while 97.9% of ¹³¹I^- removal efficiency was for consequent precipitating Mo with α-benzoin oxime, and higher than 99.9% for AG1-×8 anion exchange chromatography, about 75% for activated charcoal chromatography. After purification by the mentioned procedure for fission ⁹⁹Mo, decontamination factor (DF) of ¹³¹I^- was 1.90×10⁶. and the removal efficiency of ¹³¹I^- was higher than 99.99%. For ¹³¹IO^-₃, AgNO₃ could not precipitate iodate in HNO₃ solution. However, precipitating Mo with α-benzoin oxime could take away more than 99% of ¹³¹IO^-₃ in solution. Consequently, 99% of ¹³¹IO^-₃ in solution was removed by AG1-×8 anion exchange and nearly 70% of ¹³¹IO^-₃ was decomtaminated by activated carbon chromatography. The final DF of ¹³¹IO^-₃ was 2.52×10⁵ and the removal efficiency of ¹³¹I^- was more than 99.99% too. The experimental results showed the established procedure for fission ⁹⁹Mo production gave excellent decontamination effectiveness for ¹³¹I.