Aiming at the construction cofferdam standard of ship lock expansion project,we analyze double functions of the cofferdam based on Zhuzhou second ship lock project.The standard of cofferdam should be determined for different regions.Based on fully balancing the construction cost of diversion facilities and the loss caused by reducing standards,the flood control and storm water drainage are appropriately implemented to minimize the impact on the duration of the project.Meanwhile,we summarize the characteristics of construction diversion,the design targets of the cofferdam and the flood control measures,which can provide references to new arrangement schemes and cofferdam design for ship lock expansion project.