The useful dispartching of a reservoir is according to the reservoir design and reservoir water supply tasks,combing with the engineering facts,to reasonably determin the variety of water levels operating parameters,and on the basis of major and minor relationship between water using departments for overall consideration,to develop the reasonable dispatching scheme and the scientific deployment of water,as far as to meet the water requirements of every water using department in order to give full play to comprehensive benefit of a reservoir.By taking Gaoquan Reservoir as a case,this paper introduced the analysis and calculation of useful dispatching of a reservoir and stated the drowing method of optimizing useful dispatching graph of a reservoir.