Abstract: In order to study the deformation law of soft soil deep foundation pit in fluvial and lake sedimentary environment, taking the deep foundation pit project of a station along Foshan Rail Transit Line 2 as research object, based on actual excavation and layout of monitoring points, combined with its engineering geological conditions, a three dimensional numerical model is established, and a comparative analysis of the foundation pit retaining structure, land subsidence and diaphragm wall horizontal displacement is carried out. The results reveal that the maximum monitoring horizontal displacement of the soft soil deep foundation pit long side is 23.0~24.0 mm, that of the short side is 13.5 mm, and the displacement curve is overall arched; the land subsidence monitoring maximum value in foundation pit long side direction is 25.0 mm while that in short side direction is 14.5 m, and is 6.8 m away from pit edge with the curve showing a wide ′V′ shape; the foundation pit 3D numerical simulation results are generally consistent with the monitoring values, and the biggest deviation from monitoring value is 10% to 12%; when excavation depth reaches 7 m, the foundation pit deep soil shows heave tendency due to solidification effect and retaining structure moving inward, the heave displacement reaches 4.1 mm after the excavation is completed; through monitoring and simulation means, the deformation law of deep foundation pit construction in this type of soft soil is verified, and the deformation value didn′t exceed foundation pit deformation control limit.