In order to accurately predict the influence of foundation pit excavation on adjacent pile foundation, this paper uses two-stage method to analyze the horizontal deformation and settlement of pile foundation based on Pasternak model. In the first stage, the horizontal displacement and vertical settlement of foundation soil at the axis of pile foundation caused by foundation pit excavation are calculated by the formula. In the second stage, the Pasternak model considering soil shear strain is used to simulate the deformation of pile foundation, and the horizontal deformation and settlement of adjacent pile foundation caused by foundation pit excavation are solved by superposition method, and a simplified calculation method is proposed. Based on the monitoring data of foundation pit construction of Hengqin-Mangzhou tunnel project, the accuracy of this method is verified by comparing the calculation results of this paper. The results show that the influence of foundation pit excavation on the lateral displacement and bending moment of adjacent pile foundation is mainly within the range of 0.4 times the excavation depth of foundation pit. The influence on the settlement of the pile is mainly in the range of 0.6 times the excavation depth. The method of reinforcing the adjacent soil by supporting structure can effectively reduce the surface settlement value near the supporting structure.