Abstract: The hardening soil small (HSS) model is employed in the numerical simulation of underground engineering, effectively accounting for the nonlinear response characteristics of soils within the small strain range. Compared to other models, the HSS model provides more accurate predictions of surface settlement and structural deformation. Based on a series of laboratory tests and empirical equations, the HSS model parameters are calibrated for a typical soft soil layer in the coastal area of Taizhou. These calibrated parameters are then applied to an actual excavation project simulated in 3D FEM, and it is compared with the model using the parameters from the geotechnical report. The simulated results indicate that the parameters obtained from the laboratory tests closely match the measured values for horizontal deformation, thus validating the accuracy and superiority of the calibration method. This study provides valuable insights for predicting the deformation in underground projects in the coastal areas.