In soft soil areas where the surrounding environment is relatively more complicated, the deformation of the foundation pit will have a negative impact on adjacent structures. There are many factors affecting the deformation of the foundation pit, but factors such as structural rigidity, support arrangement (number of rows and spacing) have been determined in the design stage, and there are few factors that can be adjusted in the construction stage. The control method for lateral deformation of foundation pit during excavation are discussed from the perspective of supporting axial force and soft soil rheology. Based on the mechanical characteristics of the deep foundation pit supporting system in soft soil, the mechanical state and control mechanism of the system are studied systematically. The lateral deformation control methods for the retaining structure are proposed for the foundation pit under different conditions with and without support exposure. Meanwhile, the methods are applied to projects, and the applical results show that the method has a significant effect on the lateral deformation control of the deep foundation pit.