The construction of foundation pit adjacent to the pile foundation of a building will cause additional deformation and internal force of the pile foundation，which will affect the safety and applicability of the upper building． In view of the current theoretical research on this problem， the elastic foundation beam method is widely adopted，which simplified the pile as an Euler-Bernoulli beam resting on the Winkle foundation or Pasternak foundation． However， this method is unable to account for the shearing effect of the pile and the unevenness of the soil parameters along the pile caused by excavation． So an improved twostage analytical method was proposed，seeing existed piles as Timoshenko beams resting on the Vlazov foundation and considering both the bending and shearing effects． The results were compared with the existing research results and field monitoring data． The results show that the calculation method can accurately and effectively analyze the mechanical response of adjacent single pile under the influence of foundation pit excavation． At the same time，the selection of foundation model and the influence of shear effect of pile foundation are discussed and analyzed． It is concluded that the parameters determination of Vlazov foundation model has more theoretical basis and the model is more in line with engineering practice; and with the increase of pile diameter， the shear effect of pile foundation has a significant impact on the internal force of pile foundation．