Abstract: Swelling induced by water absorption of swelling soil results in complex swelling stress on tunnel supporting structure. In order to investigate the impact of strength declining and swelling effect of shallow-buried swelling soil on supporting structure, taking the Chenggong tunnel as the background, the relationship of shear strength and initial moisture content is verified by indoor direct shear test; based on the result of laboratory test,ABAQUS 3D finite element software is used to study the effect of soil swelling on tunnel support structure, and the impact of swelling effect on deformation of surrounding rocks and internal force of supporting structure under different buried depths is revealed. The results show that: friction angel and cohe sion decrease with an increase of moisture content, cohesion is significantly affected, the relationship between the shear strength and moisture content of swelling soil can be represented by quadratic parabola; large swelling pressure is produced due to restraint of supporting struc? ture after water absorption of swelling soil and it results in damage of surrounding rocks and increase of invert heaving and horizontal convergence of sidewall; after swelling of surrounding rocks, the axial force of primary supporting structure increases evenly, the bending moment increases slightly at haunch but largely at the foot of sidewall, and the supporting structure is in an unsafe state; swelling is largely affected by buried depth and no further swelling occurs when it reaches certain ultimate buried depth.