Abstract: A largescale system-mufti-objective decision model is presented in this paper, it can be used for optimization of successive building planning and operation of the reservoir for irrigation and comprehensive utilization. The mufti-objective dynamic programming model is solved by using a new algorithm of dynamic propramming, with changeable penalty term. The results of case study show that the mathematical model and solution tec hnique are available and the benefit obtained from optimizing operation is remarkable.