For the defect of traditional cofferdam in transformation of urban rivers, the soft cofferdam using steel pile and membrane was proposed. The soft cofferdam resisted the water pressure by the frame composed of the piles, and keeping waterproof and impervious by using the membranes. A site model was built to achieve the failure mechanism and mechanical characteristic of the soft cofferdam by destructive testing. In addition, based on the large-scale universal software ADINA，the deformation and stress of the structure under the external load were analyzed and compared with that of the field test to verify the validity of the method. Moreover, the basis for further generalization of the soft cofferdam was provided by the comparison and analysis of the field test and FEM method.
