The flow regime in energy dissipation zone is very complex in expansion and renovation projects of the high-head locks，which is related to the pulsating pressure,impact pressure,etc.It is emphasized that the influences of flow regime near the cofferdams with its layout pattern on its coefficients of sliding and pour resistance.Hydraulic calculation method of the pulsating pressure and the couple are presented,and it is used for estimating the security and stability of the earth-rock cofferdam in the Fuchunjiang lock expansion and renovation project.the pulsating pressure and impact pressure on the caisson overtop cofferdam are analyzed,and the coefficients of sliding and pour resistance are provided.