In order to explore the horizontal deformation law of adjacent pile foundation under tunnel excavation, an analytical method of horizontal deformation response of adjacent pile foundation is proposed. Firstly, the free-soils displacements induced by tunneling can be calculated by Loganathan formula. The Euler-Bernoulli beam is applied to simulate pile and the Kerr foundation model is used to simulate soil-pile interaction, then the horizontal force equilibrium of the existing pile can be established, later the analytical solution of horizontal deformation of pile can be obtained. Compared with existing finite element GEPAN data, the calculating result of the proposed method can be verified. Compared with existing theory solution, this method is closer to finite element GEPAN data. The parameters results show that the depth of horizontal maximum deformation position of pile will increases with increment with buried depth of tunnel and the maximum displacement of pile is increasing. The horizontal deformation of adjacent pile has increases with the increment of ground lose rate. Horizontal displacement of pile foundation decreases with the increase of horizontal distance between pile foundation and tunnel, but the depth of horizontal maximum deformation position of pile will decrease with the increment of tunnel-pile horizontal distance.