In response to the problem of shields that underpass the existing buildings, the Nantong Metro Line 1 interval, from the East Huancheng Road Station to the Intermediate People's Court Station, which underpasses the old residential area of the Community Sendadi-Huayuan, was taken as the research case history. Based on the site settlement monitoring data, the impact of shield tunnel construction on the settlement of the adjacent buildings foundations was analyzed. Numerical simulations, taking into account the upper building load and the shield construction disturbance to the surrounding rock, were performed. The pattern of building foundation settlement was summarized. The results show that when the shield machine is tunneling in highly water-rich sandy soil and chalky soil, the head of the shield machine is prone to twisting due to soil disturbance and the dissipation of pore water, which causes instability in the excavation process and eventuallyresults in surface settlement. By setting a reasonable value of soil pressure, maintaining the balance of the digging surface, making the shield machine pass as smoothly as possible, while performing a grouting well, and filling the gap between the lining and the strata, the surface settlement caused by the shield can be effectively reduced.