The main components of synthetic detergents are the surface-active agent and detergent builder. In this paper, an introduction is given to the harm of phosphor in sodium- tripotyphosphate, a main component of detergent builder, to water bodies. By measurement of water quality indexes, the type of eutrophication in the Erlong Lake in Siping City of Jilin Province is identified, and the ratio of phosphor from detergents to the total amount of phosphor in the water body of the Erlong Lake is calculated. The re...