Abstract: In this paper, the absorption, transfer and accumulation law of phenol and cyanogen in the water-plant system polluted by phenol and cyanogen and the plant Eichhornia crassipes that can be used for purifying water have been studied.Eichhornia crassipes can absorb and accumulate phenol and cyanogen in the water. By the analysis of phenol and cyanogen concentrations in water, it showed that the mean removal rates of phenol and cyanogen in water were 56.7% and 34.1% respectively, the highest were 85.1% and 52.2% respectively. Therefore the water quality is improved markedly. The content of phenol in different organs of Eichhornia crassipes is leaves>roots>stems, but the content of cyanogen is roots>leaves>stems. It is positive correlation between phenol and cyanogen contents in water and the permeability of the leave cell membrane. It shows that the degree of damage of the leave cell membrane increases correlatively. It is also positive correlation between the phenol and cyanogen contents in water and the activity of peroxidase of the plant. It shows the resistance of plant to phenol and cyanogen pollutant in water is related to the activity of peroxidase of plant.The phenol and cyanogen pollutant in water partly is absorbed and accumulated by Eichhornia crassipes, partly is adsorbed by roots of Eichhornia crassipes, partly is deposited onto the bottom of water.