Concrete bracing is widely used in the support system of deep foundation pits. During the construction monitoring of foundation pits, the change of the axial force of the bracing is usually used to evaluate the stability of the foundation pits. However, there are many factors that cause differences between the measured axial force and the designed axial force. On basis of the monitoring of the axial force of the concrete bracing of the foundation pit of Guangji station on No. 1 Line of Suzhou Metro, the retaining structure excavation method and insitu construction situations, the author analyzes the monitoring results of the axial force of the concrete bracing in detail, summarizes the main factors that cause dramatic changes of the measured values and makes suggestions on the optimizing of the calculation of the axial force of the concrete bracing.