Abstract: In this paper, we have studied the monitoring and purifying ability of Eichhornia crassipes, Typha angustifolia, Phragmites communis, Nymphoides peltatum, Hydrilla verticillata on arsenic, mercury and cadmium in wastewater. The effect of temperature, and pH values of culture solution on the vascular aquatic plants were also investigated. The water hyacinth was considered to be a monitor and purifying plant of arsenic. It also contains mercury and cadmium Phragmites communis and Typha angustifolia are the more resistant plants to these heavy metals, and those metals can be absorbed and accumulated by these plants. The toler ance to arsenic, mercury, cadmium of the aquatic plants is related to the life forms of plants. The sequence of tolerances is as follows: Emerged plants. Free-floating hydrophytes. Floating-leaved plants>Submerged plants. The sequence of accumulation of metals in living plants is as following: Submerged paints> Floating-leaved plants>Free-floating hydrophytes. Emerged plants. The absorptance of metals by plants is affected by the temperature and pH value of culture solution.