Abstract: A shell element model instead of beam element model is used to study the in-plane eigen buckling behavior of I-sectional arches with web openings subject to radially uniformly distributed load. More accurate eigen buckling loads and buckling modes of circular arches with web openings are obtained, including three typical eigen buckling modes. The optimization of the radius of openings and the gap between openings is performed based on a modified eigen buckling load, which corresponds to arch efficiency. Parameters such as the rise-to-span ratio, the slenderness ratio, the radius of openings and the gap between openings are investigated, and their effects on eigen buckling loads are discussed. Finally, a formula for calculating the eigen buckling load of I-sectional arches with web openings is proposed, in which two coefficients k and α reflect all parameters' effects.