Curved composite bridges and curved steel bridges have already been constructed around the world;however,the calculation for shear buckling of curved bridge webs generally uses the equations for straight bridge webs or just introduces a modification factor for bridge design.In this paper,the curved bridge web is equivalent to an isotropic cylindrical flat shell,and the double triangular series satisfying four-edge simply supported boundaries are used as the displacement function of the shell.Then by means of the Galerkin method,the analytical formula for elastic shear buckling stress of curved bridge webs is deduced.The parameter studies show that the shear buckling coefficient k_c of curved bridge webs is positively correlated with the parameter h²/（Rt）,and negatively correlated with the length-height ratio l/h.This implies that the elastic shear buckling stress of a curved bridge web is larger than that of an equivalent straight bridge web.For a curved bridge with the parameter h²/（Rt）less than 2,the amount of increase is less than 4.5%.The elastic shear buckling stress of curved bridge webs can be estimated conservatively as the webs in straight bridges.While for a curved bridge with larger h²/（Rt）,using the equations for straight girders to calculate the elastic shear buckling stress is too conservative.The proposed formulas provide a more accurate estimation for shear buckling stress of curved bridge webs.