Abstract: Selenium is a rare and scattered element.There is few content in any kinds of geochemical samples.The element is difficult to form independent minerals of itself,but scattered in other minerals and media.In early years,people know only the plisonous nature of selenium and its chemical compounds.Until 1950s,selenium was recognized to be an essential element for animal and man.It has drawn attention of researchers from different fields in medical science,earth science,agriculture and biology.At present,selenium is widely used in glass making,metallurgy,electronics industry,national defense,chemical industry,medical science and agriculture.