The rational cross-sectional form of the four-center circular highway tunnel contributes to enhancing the stress state of the lining structure，reducing cracks in the composite lining，and enhancing the durability of the tunnel structure.Utilizing the Ansys APDL programming platform and guided by the design principle of continuous-curvature，a parametric modeling equation for the geometrical dimensions of local tunnel shape in arch foot area was established.The calculation method and numerical simulation models for the equivalent mechanical parameters of the anchor reinforcement area were also developed.The study revealed the impact of the local tunnel shape parameter design in the arch foot area on the internal forces of the lining structure in the four-center circle highway tunnel.It is demonstrated through practical engineering research that radii and lengths of the tunnel's arch foot arc and middle wall arc significantly affect the internal forces of composite lining structure，with increasing the radius of the arch foot arc most prominently restraining plastic zone development in lining structure.It is recommended to prioritize controlling lining tensile stress for local shape optimization to mitigate the risk of lining structure cracking.This approach provides a theoretical basis for the shape optimization of the Pijialing Tunnel，analyzing the sensitivity and influence rules of the extreme values of inner forces on the lining structure concerning the central angle of the middle wall arc （θ2），central angle of arch foot arc （θ3），and the radius of middle wall arc （R2）.