Abstract: The purpose of this research was to understand the effects of As and Ca concentrations(As: 0 and 0.2 mmol/L;Ca: 0.03 and 5 mmol/L) on cellular ultrastructure,Ca localization and elemental subcellular distributions in Pteris vittata L.,an As-hyperaccumulator.When the plants were grown in a nutrient solution without additional As,the As concentration in each fraction decreased in the following pattern: cell wall > cyplasmic supernatant > cell organelle.However,most of the As was localized in the cytoplasmic fraction of the pinna in plants treated with 0.2 mmol/L As.The results suggested that the plant cell of pinna had been capable of self-improvement when it was intimidated by arsenic.In all the treatments,subcellular distribution of Ca present similarly as: cell wall> cytoplasmic supernatant >> organelle.When the plant was grown in a nutrient solution with 5 mmol/L of Ca,the cellular ultrastructure was damaged and plasmolysis was appeared.As toxicity to the plant was strengthened by high addition of Ca, therefore the cellular ultrastructure was heavily damaged and it resulted in a decrease of As accumulation by the plant.