the pit excavation causes uneven deformation of the underlying subway tunnel, and the excessive deformation will cause the tunnel to be destroyed. Based on the existence of soil improvement problems in the actual project, a pit bottom and sidewall unloading model considering soil full reinforcement is introduced, this model is used to calculate the additional stresses on the underlying operating tunnel caused by the unloading effect of the pit excavation. On this basis, the Timoshenko beam placed in the Lifking foundation model is used to consider the effects of tunnel shear effect and soil continuity and the differential equation of tunnel deformation is established, and the finite difference method is used to solve the differential equations, so as to obtain the expression of tunnel longitudinal deformation matrix. The proposed method is compared with the measured engineering data to verify the accuracy and applicability of the proposed method. The results show that, compared with the degradable Winker foundation model of the proposed method, the Lifking model considers the continuity of the soil, it is closer to the measured data.