It is common to have a foundation pit accident, when failing to deal with the effect of confined water. In order to avoid such accidents, the Jiangnan launching shaft of Qingchun Road River-Crossing Tunnel in Hangzhou was investigated. According to the analysis of on-site monitoring data of wall deflection, settlement, and strut load, some conclusion can be drawn. Firstly, the wall deflection is closely related to the plane size of the foundation pit, and through strengthening the stiffness of the central support, the wall deflection can be greatly controlled. Secondly, the maximum settlement point is 0.5 times depth of the excavation away from retaining wall. Finally, load in the first level strut gradually decreased during the construction, and even can turn to be tensile force.