Irrigation by continuous flooding could result in a distinct decrease in the cadmium (Cd) content of brown rice grown in paddy soil polluted by cadmium. The effect of water management on the mechanism and rate of uptake and accumulation of cadmium by rice was studied using rice pot experiments combined with analysis of the characteristics of membrane coated outside the roots of rice growing in two types of paddy soils polluted by cadmium in Hunan Province in 2005. The results showed the amount of Fe(Ⅱ) and Mn(Ⅱ) absorbed by the root coating of rice increased with the duration of flooding and the depth of water in the paddy soils. The Fe(Ⅱ) contents of the root coating of rice grown in Alluvial Loamy Paddy Soil (ALPS) and Yellow Clayey Paddy Soil (YCPS) irrigated by continuous flooding (FI) treatments were increased by 12.6 times (p<0.01) and 8.5 times (p<0.01), respectively, compared with corresponding controlled moisture irrigation (CI) treatments. Correlation analysis revealed significant linear relationships between the content of ferric oxides Fe(Ⅲ) and ferrous Fe(Ⅱ) in the rice root coating for the different water management treatments. The Fe(Ⅲ) content in the root coating of rice grown in the two types of paddy soils with the FI treatments increased by 1.5 times (p<0.01) and 1.0 times (p<0.01), respectively, compared with the corresponding CI treatments. The cadmium contents in the root coating from the two types of paddy soils with the FI treatments decreased by 77.9% (p<0.01) and 50.3% (p<0.01), respectively, compared with the corresponding CI treatments. The different irrigation treatments resulted in a strong negative relationship between the content of cadmium and that of both Fe(Ⅱ) and Fe(Ⅲ) in the root coating of rice. Compared to the CI treatments, the FI treatments in paddy soils also resulted in distinctly lower cadmium contents in the roots, straw and brown rice. The average cadmium contents in brown rice grown on the two paddy soils with FI treatments were decreased by 41.3% compared with the intermittent irrigation (II) treatments, and were decreased by 70.7% (p<0.01) compared with the CI treatments. The cadmium content in the brown rice had a strong positive relationship with the cadmium content in root coating, but a remarkably negative relationship with ferric oxides in root coating for all water management regimes. Conclusively, we deduced that the competitive adsorption of metal cations like Fe²⁺ with Cd²⁺, and the co-sedimentation of S^2- and Cd²⁺ increased greatly under the reductive condition of the continuous flooding irrigation water in acid paddy soil polluted by cadmium, which significantly reduced the bio-availability of cadmium in the soils.