Higher aquatic plants are known to accumulation and bioconcentrate heavy metals, while works dealing with fern are still very scarce. In this study, cadmium (Cd) accumulation and its influence on mineral nutrients, photosynthetic pigments and Fv/Fm, enzymatic and non-enzymatic antioxidants, protein content and ultrastructure of Salvinia natans (Linn.) All. plants exposed to 2.5，5，7.5 mg/L and 10 mg/L Cd for 7d were analyzed. It was found that, with the rise of the Cd concentration in culture medium, (1) Cd content increased in a concentration dependent manner. (2) Cd resulted in serious imbalance of nutrient elements, and promoted the adsorption of Ca and prohibited the adsorption of P, K and Na significantly. (3) Chlorophyll content and chlorophyll fluorescence Fv/Fm showed a decreasing trend. (4) Cd treatment led to the disorder of content/activity of antioxidant systems. A significant reduction in SOD activity was observed in Cd treated S. natans, in contrast, an increase was also noted in POD and CAT activity, levels of GSH, AsA and Car followed by a decline. MDA content increased evidently with augment of Cd concentration indicating the occurrence of oxidative stress. (5) Soluble protein content was found to be decreased at all the Cd concentration. (6)TEM observation revealed that Cd impaired the organelle ultrastructure obviously, such as swelling and disorganization of chloroplasts, decrease of cristae quantity and vacuolization of mitochondria, disaggregation of nucleolus, breakage of nuclear envelope, disappearance of karyoplasms, and appearance of crystal. Results suggest that S. natans was able to accumulate Cd, the correlation of dose-effect was significant between the toxicity and concentration, and Cd caused oxidative damage as evidenced by increased lipid peroxidation and decreased chlorophyll and protein contents. Cd pollution destroyed the physiological and ultrastructural foundation essential for normal growth and metabolism of plants. SOD could be served as a molecular biomarker of oxidative pressure imposed by Cd pollutant and a sensitive eco-toxicological indicator to evaluate Cd pollution on water environment, its 50% effective concentration (EC50) for 7 d of exposure was 2.41 mg/L; the maximum permissible concentration (MPC) was 0.241 mg/L.