Given the large deformation of large-span non-latticed column steel support of metro deep foundation pits, which affects the safety of the foundation pit. Taking the metro deep foundation pit project of Ci-Ge-Zhuang station of Beijing Da-Xing International Airport Express as the research object, through theoretical calculation and field measurement, this paper analyzes the deflection of steel support during the construction process, summarizes the important factors affecting the steel support deflection, and puts forward the corresponding control measures. And last, through comparison and verification, a fast, economic, and effective method to reduce the deflection of steel support is found, which effectively ensures the safety of the foundation pit, and provides a useful reference for the design and construction of similar projects.