Abstract: How to secure safe operation of flood releasing works and their scour prevention measures and to less affect downstream flow pattern and dyke protection structures during floodreleasing in cofferdamretaining generation period of TGP is an important problem needed to be solved. It deals with series of hydraulics problems relating flood releasing regulation and other measures. This paper presents the test results on flood releasing obtained from a hydraulic model with a scale 1∶100. Through the optimazation of schemes the proposed operation mode is the case that 22 deepoutlets are opened,i.e.,No.23 deepoutlet being closed, and all bottoon outlets opened, its floodreleasing discharge may reach up to 68 530m3/s,the safety of scourprevention installations and downstream cofferdam may be secured. By optmizing the regulation of bottom and(or) deep outtets and in combination with a certain lowering the water level before Gezhouba Project, the undesirable phynomena of water jet striking the hingedsupport of tainter gates can be avoided in the cases of Q≤60 000 m3/s.