The desalination industries are considered to have a major role in developing human life. Recently this technology became widely distributed, and its construction along the coastal area has been widely reported. Many countries are adopting these technologies for securing the fresh water supply for consumer consumption all over the world. This situation has raised the need for researches to evaluate the. Environmental Impact Assessment (EIA) of these technologies on coastal line environment. This study has been directed to monitor sea water quality used for feeding desalination plants to determine the concentrates of selected pollutants such as heavy metals by using chemical monitoring system to know their effects on the desalination units and other components. This study was conducted in the year 2003 from January to June Samples were collected from feed water intake of Benghazi North Desalination Plant and Tobrouk Desalination Plant, both plants were chosen because of their importance for supplying fresh water for potable water and industrial uses. The results of this study showed monthly differences in most tested parameters, these differences lead to the scale and corrosion by precipitation on the components of the desalination unites. The objectives of this study is to know the main reasons which caused increasing these concentrates in the sea water (study area) and know how to deal with.