Lateral displacement of soil will occur when the artificial hard shell mixed pile composite foundation is loaded, which will deform the pile foundation near the bridge and reduce the stability. In order to analyze the influence of embankment filling on adjacent bridge pile foundation in deep soft soil area, the pile deformation under different foundation treatment methods is analyzed by formula derivation and finite element numerical calculation method. Based on Winkler's elastic foundation beam theory and two-stage analysis method, the controlling equation of pile-soil interaction under embankment filling condition is derived, and the pile deformation and internal force changes caused by soil deformation under different foundation treatment methods are calculated, and verified by field tests. The results show that increasing the thickness of the hard shell, elastic modulus of the hard shell and decreasing the distance between the stirred piles are beneficial to controlling the pile deformation and bending moment. In the pile foundation inside the embankment, the deformation of pile body can be controlled by changing the thickness of hard shell. The pile foundation at the edge of the embankment can be controlled by changing the elastic modulus of the hard shell. The pile foundation outside the embankment can be controlled by changing the distance between the stirred piles.