With the rapid social economic development, the ecological environment in Wuxi city has been worsened during the past 20 years, the pollution of water resource is especially serious and the water quality was decreased by one class in every 5 to 10 years.This paper studied the main factors and reasons of the effects of the social economic development on the water environment, especially Taihu Lake.Some measures to improve the water environment are suggested, i.e., the adjustment of industrial structures, improvement of recycle utilition rate of water resources, administration of sewage in the market economy and environment education to the people and so on.