Taking a 24.09-m-deep foundation pit of Shanghai Metro Line 1 which uses the semi-reverse construction process of “three open excavating-one tunneling” as an example, through gathering and analyzing field monitoring data and making use of forward and back analysis methods, we found out deformation laws of foundation pit under the construction of semi-reverse method.The implementation results of this project indicated that the semi-reverse method is an effectiveway to improve rigidity of the exterior support, control the deformation of excavation, and ensure safety of the surrounding buildings and pipelines. Meanwhile, the results coincide essentially with time-space effect. The deformation of the excavation is closely correlative with excavation speed and exposure time. It provided some useful reference for the design of deep excavation in soft soil.