Abstract: In response to the risk of excessive deformation during the construction of deep foundation pits in deep soft soil layers in Hengqin, a practical engineering project was taken as the research object. Combining multi-source monitoring and numerical simulation methods, the deformation evolution law and deep sliding failure mechanism of the support structure and surrounding soil were systematically analyzed. Research has found that the settlement of the silt layer on the east side of the foundation pit is significantly affected by the dynamic changes in the water level of the drainage channel; The stiffness of the support structure is weakened due to the rheological properties of soft soil; The shear strength of the passive zone soil continues to decrease, forming a through slip surface. Based on the above incentive analysis, this article proposes an emergency response technology of "dynamic backpressure+step-by-step closure". This technology effectively controls the deformation rate and successfully mitigates the risk of foundation pit collapse through comprehensive measures such as soil back pressure backfilling, crack grouting sealing, and rapid sealing of the cushion layer. The study verified the applicability of information technology dynamic control in soft soil deep foundation pit engineering, and constructed a deformation prevention and control system including warning indicators, stiffness compensation, and emergency timing, providing theoretical support and practical reference for risk control in similar engineering projects.