This paper mainly gives a review on the concept of the eutrophication in water system and the pecuniary loss caused by it (e. g. Red Tide, Water Bloom); Then it puts forward the reason why we must ban phosphorus, the function that we add phosphorus into traditional synthetic washing powder, and the course of eutrophication in water system caused by phosphorus after it runs into water system. With the exception of that, the thesis introduces the standard that we judge the eutrophication in water system and the situation of phosphate banned at home and abroad nowadays.