At present, the calculation of the external surface settlement of the deep foundation pit is based on the premise that the soil is an ideal undisturbed soil. This does not match the actual project. The external surface settlement of deep foundation pits cannot be well characterized. Aiming at this problem, an improved calculation method for ground settlement of deep foundation pit support is proposed. Firstly, based on the theory of damage soil mechanics, a soil damage model is established. Then, using the soil evolution and constitutive relation under the damage condition, the calculation model of ground settlement supported by the foundation pit is constructed. The experimental results show that the model can well describe the settlement process of the supporting ground surface in deep foundation pit engineering, which is consistent with the engineering practice monitoring results. The experimental results also prove that soil damage and surface overload have a great impact on the foundation pit support.