The principles and benefits of the physic-ecological engineering (PEE) for improving drinking water quality in a lake are dealt with a sample experimental engineering in water source area of Mashan Drinking Water Plant of Wuxi City in Taihu Lake. The PEE may be used in principle for different conditions of depth, water quality.bottom sediment and wind wave.The PEE has its main objects of reducing algae concentration and improving the hydrochemical indecies of water quality in enclosed intake area of a water supply plant, including two parts of physical and ecological engineering. During the experiment of two years, the technology and management of the PEE have been much improved and experienced many time of storms and strong wind waves.The PEE may effectively reduce the algae concentration and improve the water quality. The mean rate of reducing algae concentration is more than 59-78%;the rates of reducing of turbidity and concentrations of TN,TP,NH₄⁺-N,BOD₅ and CODM_Mn are 9—40%,24—45%,2—24%,5—70%,9—61%,and 10—25% respectively. Using a special technology, the Eichhoma irassipes solms may maintain its growth under strong wave condition on the open lake surface,and its productivity in summer accounts 507 g/(m₂·d), which lead to purifying the water and restrain the algae growth. The PEE may reduce the chlorine expenditure and increase the drinking water output without the limitation caused by water bloom in lake.