A biological pond system was constructed by Typha angustata, Canna glauca, Hydrilla verticillata, Myriophyllum aquaticum, Arundo donax, Iris tectorum, Eichhornia crassipes to investigate the accumulation and tolerance of cadmium in aquatic plants. The subcellular components and different chemical forms of cadmium in plants was separated by differential centrifugations and fivestep extraction. Then, the cadmium content was determined by atomic absorption spectrophotometry. The results showed that: (1) the cadmium accumulation was much more in root than in stem and leaf. Furthermore, the cadmium concentration of 3 kinds of aquatic plants: submerged plant（Myriophyllum aquaticum, Hydrilla verticillata）> floating plant(Eichhornia crassipes) >emergent plant（Typha angustata, Canna glauca, Arundo donax and Iris tectorum). (2) The subcellular components of H. verticillata, E. crassipes, A. donax displayed the following sequence: cell wall＞protoplast＞mitochondri＞soluble fraction, which proportion was 37.16%-50.86%, 20.69%-31.21%, 10.81%-23.83% and 8.15%-19.83%, respectively. (3) The greatest amount of cadmium found in 1 mol·L^-1NaClextractable fraction and H₂Oextractable fraction, the two chemical forms relative contents in percentage were 29.37%-56.27% and 15.06%-36.19%, respectively. The analysis indicated that the cadmium accumulation ability in M. aquaticum, E. crassipes, C. glauca, A. donax was better than in T. angustata, I. tectorum, H. verticillata., and cadmium mainly existed in the cell wall and vacuole of the root of the aqudtic plant with the binding state or adsorption state of pectinate protein to attenuate the toxicity of cadmium to the root organelles and the plant overground.