Abstract: The optimal operation of reservoir is the key of reservoir management and complicated process．This is a complex environmental decision making problem due to the presence of multiple objectives stemming from multiple uses of the reservoirs such as inflows，water demand，evaporation，power generation etc.A multi-objective decision support system of the optimal operation of reservoir is designed which is consists of four modules such as Database，Model base，Method base of operating policies and User operation.It sets up the goal-programming model based on economic cost function and utility function relying on decision maker’s preference to provide flexibility and optimal operating policies.