Abstract: A deep and large foundation pit project in Xiangcheng District, Suzhou has the characteristics of large area, irregular outline, diversified excavation depth, and it’s construction period is tight. According to the characteristics of the foundation pit, a partition excavation plan is proposed, which is divided into A, B and C three areas, the excavation sequence of these three areas is clarified. According to the surrounding environment of the site and the excavation depth of the foundation pit, a targeted enclosure system is adopted. Area A adopts the cantilevered enclosure form of bored piles, and area B, C adopt enclosure form bored piles combined with an internal support. Different types of support systems are compared and analyzed in aspects of economy, construction period, earthwork excavation, etc. Based on the analysis results, targeted support forms are adopted for area B and area C, area B adopts the ring support form, area C adopts the truss support form. The targeted support form improves the efficiency of earth excavation and saves construction time. According to the actual monitoring data of the project, the internal force of the support system is within the controllable range, and the deformation of the foundation pit is small. The combined application of ring support and truss system has achieved good implementation results in engineering practice, which can provide a reference for the design and construction of similar deep foundation pit projects.