Abstract: Controlling the lateral deflection of retaining wall has become a core problem in deep excavation, and lateral deflection during bottom excavation occupies considerable proportion of that in the whole excavation works. Based on measured data and factual work of a metro station construction in shanghai, the bracing effect of concrete cushion is analyzed. As a result, the exposure time of excavation has notable influence on the retaining wall's lateral deflection during the period of bottom excavation. In addition, concrete cushion plays bracing function on controlling lateral deflection of the retaining wall, which is similar to the reinforcement concrete bottom plate. Accelerating the construction of concrete cushion as soon as possible can make full use of bracing effect on controlling the lateral deflection of retaining wall. Bracing effect of concrete cushion depends on several factors, such as concrete cushion's strength, stiff and flatness. The effect can be weakened with debasement of concrete cushion's entirety. Some proposals for lateral deflection controlling during bottom excavation of deep pit are offered. Shortening bottom construction time is favorable of lateral deflection controlling. Increasing concrete cushion's entirety and fastening construction progress of the reinforcement concrete bottom plate can reduce retaining wall's lateral deflection on the excavation stage. The results may be reference to other deep excavation engineering.