The deep soft soil foundation has great influence on the supporting structure of deep foundation pit,and whether the support design is reasonable or not is directly related to the safety and economy of foundation pit excavation.In this paper,combined with an example of a LNG project,the stress of the supporting structure of deep foundation pit on soft soil foundation is analyzed and discussed.The influence of the thickness of foundation pit bottom plate and the bending angle of supporting wall on the force of supporting structure is emphatically studied,and the force transmission distance of the internal support is analyzed.The problem that should be paid attention to the design and construction of flexible support was summarized,which could provide a reference for the design of similar support structure.