This paper presents an approach to the reservoir operation for flood control purpose in real time on the Vu Gia-Thu Bon River. The real-time operating method for reservoir system based on reservoir simulation modeling system Vu Gia - Thu Bon River set by the author that integrate components includes rainfall runoff, numerical models in river systems and flood regulating model for reservoir system. The simulating results apply for a big flood in 2009 for 5 reservoirs (Song Tranh 2, Song Bung 2, Song Bung: 4, Dak mi 4 and A Vuong) in order to regulating the flood at the downstream.