Hylotelephium spectabile with high tolerance to cadmium (Cd) might be a potential candidate for phytoremediation. However, the mechanisms for Cd accumulation and tolerance in H. spectabile are poorly understood. Four H. spectabile populations, namely HB1, HB2, JS, and LN, were selected to investigate their Cd extraction potential and the underlying mechanism of Cd accumulation, focusing on subcellular distribution and antioxidant enzymes. The Cd concentration, bioconcentration factor and transfer factor of the LN was significantly higher than other populations, particularly with increasing Cd exposure, and no obvious growth inhibition observed. Segregation of excessive Cd to Cd-rich granule in LN was much higher than other populations which reveal one possible mechanism of Cd accumulation. A significant increase in superoxide dismutase (SOD) and catalase (CAT) activities with increasing Cd stress suggested SOD and CAT contribute to the Cd tolerance of H. spectabile. LN displayed significantly higher and constant peroxidase (POD) activities than other populations, which indicated that an effective mechanism existed in the LN to cope with Cd stress. Therefore, the subcellular distribution and antioxidant enzymes might play important roles in Cd accumulation and tolerance of H. spectabile. LN possessed high Cd extraction potential, and further studies under field conditions are warranted.