First, a method of calculating risk rate on pre-storage level is introduced based on analyzing the necessity and major difficulty to heighten storage level as well as its benefit and risk for a reservoir flood control. Next, a fuzzy control model and its corresponding algorthm are presented by using fuzzy set theory. There exist two goals such as economical benefit and risk in the process of heightening storage level of a reservoir. The pursuant message is provided by this model for decision-maker at the flood period, which is necessary to decision maker to heighten the water level at stages or realtime control. Finally, the fuzzy optimal control model is applied to Fengman Hydropower Station. It is shown that the model and foe algorithm are rigorous and simple, and can also be applied to other hydropower stations.