Abstract: The treatment method for simplifying design shape of bend pipes at tunnel portals is proposed based on the restrained conditions and stress analysis of tunnel crossing pipeline at tunnel portals, the force balance equation after simplifying bend pipe parameters is derived, and the equation to derive the calculation method of pipe wall stress σ_Bmax under maximum bending moment is used. The maximum calculated stress can be used to select or check the wall thickness of bend pipe and ensure the bend pipes are safe and reliable. The calculation results can comprehensively reflect the actual situations in the construction and installation phases, and embody the engineering parameters of pipeline construction and installation within the tunnel, so the model is conducive to the control of engineering quality.