In order to clarify the characteristics of the retaining system of narrow-long deep foundation pit in soft soil in Nansha Port Area, the behavior of retaining system for foundation pit excavation was studied, according to the measured data of Guangzhou deep and narrow foundation pit with diaphragm wall and internal support as retaining system. Results show that the maximum lateral wall displacement ranges from 0.07%H to 0.38%H, with a mean value of about 0.22%H, where H is the excavation depth. The location of the maximum wall displacements H_δm is between H?6 andH+3, and most are above the excavation surface. The wall deformation mainly occurs in the excavation stage of the second and third layers of soil, accounting for 32.6% and 40.1% of the cumulative deformation respectively. Foundation pit excavation has depth effect, and layered excavation of deep foundation pit is very important for wall deformation control. The main influence depth of wall deformation is about twice the excavation depth of foundation pit, and the spatial effect is significant. The variation characteristics of the vertical reinforcement stress and the lateral displacement of the wall are basically similar. With the excavation depth of the foundation pit, the maximum position moves down gradually, revealing the dynamic adjustment process of the wall deformation and stress. The axial force of the support reaches the maximum value after about two weeks after the support is erected, which shows real-time with the excavation of the foundation pit. The axial force of the multi-layer support structure is adapted dynamically with the excavation and support process of the foundation pit to coordinate the deformation development. When the excavation of the foundation pit is completed, the ultimate stable axial force of reinforced concrete support is about 0.73 times of the design value, the axial force of the first and the second steel support is 0.40 and 0.31 times of the design value, and the steel support design is conservative. On the premise of ensuring the stability of the foundation pit, the optimal design of a support scheme can be considered. Research results have important practical significance for the subsequent safety prediction of similar foundation pits in this area, as well as the guidance of similar engineering design and construction parameter optimization.