Abstract: This paper presents a stochastic waste water quality management model. This model finds the economically optimized treatment efficiency for each discharge source along a river while maintains the risks of water quality in the river below prescribed bounds..It takes into account over all the amount of effluent waste,diffusion,mixing processes of the waste in water,and especially,the stochastic property of the river flow,and gives the optimal beneficial result both environmently and economically. This model was applied to Tuojiang basin in Sichuan Province.