Abstract: The relation between quantity of pollution discharge and river water quality is one of key technical problems that environmental management urgently wants to solve. The authors explores the mechanism of a combined monitoring system for point systems,river outfalls and control river stations,analyzes the river coefficient of the pollutant at the point source to the river,and the influence coefficient of the pollutant at the river outfall to the river station,and finally get the contribution coefficient of pollutant at the point pollution source to the control river station. This is the important technical support of dynamically managing point sources to assure water quality to reach the standard.