The Mori-Shisen tunnel located at Isogo-ward, Yokohama-city is a twin tunnel with center pillar. Its length is 164m and cross-sectional area is 121 m2. Since overburden is low and structures exist on the surface, auxiliary methods of construction, such as a Trevi-tube method and horizontal jet grouting at leg level, were applied for the purpose of controlling subsidence at the surface to the minimum. Moreover, construction was carried out carefully performing measurement managements and reverse analysis. Reverse analysis was performed using 2-dimensional FEM based on measurement results. Consequently, construction was accomplished successfully without any serious impacts against surrounding structures. This report describes various kinds of measurement results and reverse analysis results at the time of tunnel excavation.