Eutrophication of water bodies resulted by the unbalance of internal nutrient structure in the ecosystem, which drives the biological variety and quantity to evolve against the ecological balance. Toreduce the discharging of the nutrients will be one of the most basic and the most effective approaches to control waterbody eutrophication. The traditional viewpoint and recent studies showed that phosphorus would be the limiting factor for algal bloom producing under certain conditions. In this paper, the important drinking water source of D watershed in the Pearl River Delta was chosen as the investigation case, and the phosphorus dynamic process and its ecological response were studied. The core issue of nutrient control was focused and the dynamic studies on phosphorus pollution of the whole watershed were conduced: 1) to highlight the non-point source pollution control, which is the difficulties research subject of water resource protection; 2) to perfect the calculation method for phosphate input and output, providing important basis on decision making for nutrient control; 3 ) to establish database and water quality model, to predict the water quality response after different phosphorus control schemes realized; 4) to determine admissible phosphorus loading and control standard according to the quantitative relationship between the external force function (mainly the exotic nutrient salt concentration or loading) and internal nutrient state response, and to work out the effective and practical techniques for eutrophication control.