Water lettuce (Pistia stratiotes L.) is aquatic plant which has capability to absorb heavy metal in water. In this study, the authors analyze and assess the absorption of water lettuces for highly toxic heavy metal in wastewater such as Asenic, Cadmium and Lead (As, Cd, Pb). The research results showed that water lettuces can grow well in polluted environments by As, Cd and Pb. The amounts of heavy metals were absorbed in the roots greater than in leaves from 1.2 to 5.7 times. Absorptive capacity respectively is from Cd -- Pb -- As. The ability of water lettuces to purify water polluted Pb after 5 days culture, the absorption rate was 100 percent. This water lettuce is to be used in bioassay for heavy metal contaminated water.