Synthetic sea salt is a medium formed by converting freshwater into sea water, and made of many kinds of inorganic chemical raw materials according to the chemical components of seawater. It basically contains all kinds of macroelements, microelements and trace elements found in natural sea water, without any nutrient such as N, P, Si, etc., and other elements harmful to sea creatures such as Os, Be, Tl, etc. Synthetic sea salt is pure and not contaminated, contains no organic contaminants such as surface active agent, organophosphorus pesticide, petroleum hydrocarbon, etc., which always exist in natural inshore sea water. Thus, it is preferably selected for breeding sea creatures for inland environments or places that needs clean seawater.