Dongping lake is a very important hydraulic junction of the eastern engineering of diverting water from the south to the north of China. The water quality and ecological environment of Dongping lake will make important affection on this engineering. Soil and water loss is one of the important factors which led up to water pollution. Taking Dongping lake as an example, the change of water quality of Dongping lake caused by soil and water loss is analyzed, and the countermeasures of soil and water loss on water pollution effective control are discussed.