This article introduces the cofferdam design for DSIC. Reasonable modifications were made to the design according to the problems encountered during construction, especially for the water leakage during construction of the south cofferdam. Considering the characteristics of shipyard’s main work and the site condition,this article analyzed the position of leakage and elaborated method for determining the leakage point. Based on the supplementary survey, we adopted a combination treatment of high-pressure jet grouting and curtain grouting. We also put forward detailed monitoring requirements and water pumping method, which ensured smooth accomplishment of the project.