In this paper, on determination the proportion and contribution rate of the phosphorus indetergents to the phosphorus loading in the water body, the mathematical model of Thomamn is employed to predict the response effect arising from restricting or banning phosphorus in detergents.The prediction results show that phosphorus content of the water will reduced to 0.18mg/L from the present 0.24mg/L and the phospho rus loading will decrease by 25%;if the scat tered culture of poultry and livestock in the valley pollut ion source by 60%, the water can achieve phosphorus quality standard of Class Ⅱ (0.1mg/L)of surface water.