Water quality was very good in many middle-large scale lakes and urben lakes in China before 1970s. These lakes were selected as the raw water sources for advanced treatment of drinking water and/or recreation lakes. But the eutrophication process developed rapidly and the water quality in more and more lakes is lower than the standard for drinking and recreation recently. Purifying raw water quality in lakes is an urgent problem faced in many regions for sustainable development. Some Physico-Ecological Engineering (PEE) experiments in Taihu Lake have been doing since 1991. The research results were summarized partly in this paper, including the principles for purifying water quality, the construction of the model engineering, the growth laws of some species of floating plants, the roles and effects of snail (Bellarnya aeruginosa) in purifying water quality, and the efficiency of PEE. The experiment took place in the hypertrophic bay of Taihu Lake -Wulihu Lake, in the intake area of Wuxi Zhongqiao Drinking Water Supply Plant (ZDWSP), with an experiment area of 2200m² and depth of about 1.6m. The static and dynamic pumping experiments have been doing since August 1994. The PEE may effectively remove algae and purify water quality. The mean reducing rates of PEE for turbidity, NH₄⁺-N, NO₂⁺-N, and colour are 82%, 69%, 69%, 46% respectively during August 1994-June 1995.