Abstract: In view of the pollutant control goal and economic state in China,this paper introduced an integrated accumulating contribution-benefit model,on the base of cost-effect analysis model and total emission control policy.By using this model,the cost-effective optimum installation scope can be calculated.Also,according to the minimum benefit allowance of environmental management,the scope and method to install on-line monitoring systems are determined.The data of COD discharge in one city in 1999 and that of COD discharge by major polluting sources in all-around China in 1998 are used as examples to calculate the number of enterprises and the related cost for the establishment of the systems to provide scientific basis for environmental management and decision-making.