The cofferdam project plays an important role for the protection and safe construction of the main project when the shiplock is constructed in the river.Combining with the design of a lock project,we carry out a research on a series of key technologies including the general arrangement and structural design of cofferdam in view of problems such as the complicated geological and environmental conditions,narrow construction site,etc.By the design scheme based on the research,we can not only decrease the cofferdam engineering volume and shorten the construction period,but also guarantee the safe and smooth implementation of the project.