To investigate the mechanisms of cadmium absorption and detoxicity of castor (Ricinus communis L.), two castor cultivars (ZB-8 and HB-8) were used for hydroponic experiments. The results indicated that both cultivars had a high tolerance to Cd. The investigation of subcellular Cd partitioning showed that Cd was mainly accumulated in the heat stable protein and cellular debris fractions in the leaf of ZB-8, and the biologically detoxified fraction (BDM) of ZB-8 was significantly higher than that in HB-8（P<0.01）. The contents of GSH and PCs in the xylem, phloem and leaf of the two cultivars were also determined. The results showed that GSH content in the phloem of HB-8 was significantly higher than that in ZB-8, and the PCs contents in the xylem and phloem of HB-8 were both significantly higher than those in ZB-8（P<0.01）. The higher tolerance of ZB-8 compared with HB-8 could be attributed to the higher PCs levels in the leaf. The higher contents of PCs and GSH in the xylem and phloem of HB-8 decreased Cd transport ability from the root to the shoot.