The reservoir always can't achieve its normal level for it is not allowed to store water in flood season when its limited water level is under static control . This operation will reduce the reservoir's benefit largely, and waste lots of water resource. This article takes Shimen reservoir as example, through summarizing the present situation of the static operation of limited water level, influence on the benefit of the reservoir is analyzed following this method, and dynamic control of flood limited water level is put forward to improve water use efficiency. In the actual dispatching, the upper and lower limits of the dynamic control of the flood limit are analyzed by using the pre-storage and pre-discharge method according to its hydrological and weather forecast information, and the dynamic control scheduling strategy is given. Comparing two different dispatching modes by “20110728”l flood process, the results show that when the precipitation or flood forecast is light, flood control level can be raised to 617.5m mostly to enlarge the reservoir's storage; then if the forecast is heavy, flood control level will be lowered to 610.0m to empty reservoir to keep its safety.