Abstract: A hydroponic experiment was carried out to investigate the influence of iodine species: iodide(I-),iodate(IO3-) and iodoacetic acid(CH2ICOO-) on iodine uptake by leafy vegetables(Bok-choy and Ipomoea aquatica Forsk). The results show that low level of iodine can efficiently promote the biomass of Bok-choy and Ipomoea aquatica Forsk.When iodine level in the nutrient solution from 0 to 1.0 mg/L,the iodic quantities uptaked by bok-choy and Ipomoea aquatica Forsk are enhanced with the iodine levels in nutrient solution increase.The rank of iodine species by Bok-choy and Ipomoea aquatica Forsk is CH2ICOO-I-IO3-.There is a significant correlativity between the I contents in shoots and roots of bok-choy and Ipomoea aquatica Forsk.The ratios of I contents in roots to in shoots of bok-choy and Ipomoea aquatica Forsk are roughly 2∶1 and 1∶1,respectively,which indicates the differences in iodine uptaked by plants.