On the background of 500 kV Shanghai Expo underground substation, a fluid-structure coupling FEM analysis of dewatering and excavation was made based on the Biot's consolidation theory. A pumping test was simulated to determine soil parameters by back-analysis of displacement and pore pressure. A fluid-structure coupling model was built to analyze dewatering and excavation with steady analysis method and birth-death element method respectively. Seepage and stress fields were solved at the same time. With comparison of the calculated and measured values, the fluid-structure coupling method used in the analysis of dewatering and excavation was proved to be correct and feasible.