Abstract: To deal with the extreme deformation and damage during the construction of large-span tunnels, one case study of large-span tunnel with shallow overburden, constructed by double-side drift method, is conducted, and the FEM results are verified according to the measured data. The effect of unsymmetrical support parameters of side drift on the settlement of ground surface and transfer of internal force of supports is analyzed. It is demonstrated that the Timoshenko laminated beam theory is suitable for calculating the internal force of the primary supports. The unsymmetrical support design has a great effect on the settlement of ground surface and the distribution and transfer of internal force of supports during the excavation phase of central drift. When the stiffness of inner wall is reduced to some extent, the settlement of ground surface will grow rapidly.