A test pit work was carried out in 2007 in the area of the Extension of Mariinsky Theatre. It was applied to the work to use sheet pile cofferdam. In the work large displacement of sheet pile was measured. We analyzed this work by our elasto-plastic FEM in total stress condision. In this study Mohr-Coulomb type yield function and Drucker-Plager type plastic potential were applied to constitutive equation. We decided the cohesion of each soil layer from the geological colum and the Young's modulus of the strut and sheet pile not to be able to get the detailed soil parameter and the sheet pile and strut data. For this analysis, it was obvious that the ineffective strut progressed the measured large displacement of the sheet pile.