Abstract: 【Objective】 The study was to explore the the effect of root shape and organic acid secretion on the absorption of thallium (Tl) in different rice varieties. 【Method】The hydroponic method was used to compare the amount of Tl absorption among different rice varieties. The root length, root number and organic acid secretion capacity were determined. The correlations between Tl absorption capacity and rice root traits and organic acid secretion were analyzed. 【Result】 The results showed that Tl uptake of 18 rice cultivars ranged from 55.29 to 112.01 mg/ kg, and the uptake of the variety with highest absorption capacity was two times that of the variety with lowest absorption capacity. However, there was no correlation between root traits (root length and root number) and Tl uptake among 18 cultivars. Six cultivars with high, medium and low uptake were further selected to determine their root organic acid secretion. The correlation coefficient between Tl uptake and root oxalate secretion was - 0.931 (P ＜ 0.01), which showed that root organic acid secretion effectively inhibited Tl uptake by rice.【Conclusion】Organic acid secretion from rice roots can be used as an indicator of Tl uptake capacity of rice seedlings.