This study was conducted to find out the cadmium (Cd) accumulation and tolerance of Iris pseudacorus and Acorus calamus as aquatic plants native to Korea for Cd removal in water. In the range of Cd concentration from $10{mu}M$ to $130{mu}M$, the Cd lethal dose 50 ($LD_{50}$) was $78.5{mu}M$ in I. pseudacorus and $47.6{mu}M$ in A. calamus. In I. pseudacorus, superoxide dismutase and peroxidase as antioxidants were relatively effective against oxidative stress caused by Cd, while catalase, superoxide dismutase, and polyphenolics were effective in A. calamus. The polyphenolics known as typical antioxidants were not detected in I. pseudacorus. In both species, the Cd accumulation in plants increased with the higher Cd concentration and the longer processing period. Also, the absorbed Cd was accumulated mainly in the roots. The amount of Cd accumulated in the shoot part was maximally $548.1mg{cdot}kg^{-1}$ (82.1% to Cd accumulated in the root part) in I. pseudacorus and $121.4mg{cdot}kg^{-1}$ (13.7%) in A. calamus, which implied that both species all were enough evaluated as Cd hyper-accumulators based on 0.01% or more Cd accumulation in the shoot. Especially I. pseudacorus showed outstanding ability to move well Cd into the shoots from the roots and high tolerance to Cd stress.