The project of Emergency Treatment Complex Building in Shanghai Tenth People’s Hospital is presented in this paper to illustrate the behaviors of the two-floor top-down excavation and its complicated surroundings in Shanghai soft clay. In order to restrict excavation deformations and expand construction site, the two layers of permanent floor slabs were adopted as horizontal supporting systems and the B0 slab was meanwhile exploited as working place and traffic passageway. Before construction, numerical simulations were conducted to predict the responses of the pile walls and the structure slabs. Based on the calculation results and monitoring data, it can be concluded that buildings without piles have significant impacts on the wall deflections while those with piles hardly influence the ground movements during excavation. Furthermore, the magnitude of displacements is related to the length of side and the construction loads around excavation. Buildings subside larger as their distances to excavation get closer. Settlements of buildings without piles are much more remarkable than those with piles.