Abstract: Cofferdam is the important building to ensure the wading engineering performed in the dry land.Under the influence of external factors such as hydraulic power，its running mechanism is complex.In order to effectively reflect the influence of seepage effect on cofferdam safety，this paper takes the cofferdam of some dock project for example，and processes the numerical simulation on its safety.It calculates the related parameters such as stress，displacement and safety coefficient by coupling analysis and research of the cofferdam seepage field and stress field.Study shows that the calculation result of fluid-structure interaction is helpful to ensure the safety of the cofferdam design.