Taking the Olympic Park station in Beijing 15 line as the project background, the dynamic simulation of the existing structure down－traversed by subway station is performed by 3D numerical model vs. site measurement. The results show that: the rate of upper small pilot tunnel excavation is 69.3% of the total surface subsidence, the upper small pilot tunnel excavation is a key step in the existing structure down－traversed by subway station of subsurface excavation station; The suggestion measures are advanced grouting, short footage and tough supporting; crown beam on pile and steel－pipe column applied timely; the maximum surface subsidence is located at the station midline, the range of influence is 40 m at the station both sides; after the subsurface excavation completed, The maximum vertical displacement of the structure of existing tunnel is 11.06 mm and is meet the requirement of Technical code of maintenance for city bridge.