Water hyacinth (Eichornia crassipes.) is a common aquatic plant that grows widely distributed in many region of Thailand. Its ability to absorb other elements from the water has made it possible to use it for water purification purposes (e.g.Chigbo et.al.1982). The uptake of heavy metals in this plant is stronger in the roots than in the floatings shoots (Jana 1998, T.Kamwng). The purpose of this study were to detect the residure metals by using X-ray Spectrometry and measure the amount of residue found in the water hyacinths.