Abstract: Large section lining segments are widely used in drainage tunnels, underwater tunnels and other fields in water resources and hydropower engineering.The manufacturing errors and local imperfections caused by piling and operation will influence the bearing capacity of the segment lining structures.For this reason, a calculation method for the nonlinear bearing performance of large section segments considering initial imperfections was proposed.Aiming at two typical imperfections, out-of-flatness imperfection mode and radial dislocation imperfection mode, through considering different imperfection amplitudes, local imperfection mode and imperfection distribution, we analyzed the ultimate bearing capacity values of large section lining segments.The results show that the local geometric imperfections mainly have adverse effects on the bearing capacity of segments, and the corresponding loading coefficient is affected by different imperfection amplitudes, with a variation trend of linearly increasing first, nonlinear gently increasing and coming to a convergence.For the local geometric imperfections, the influence is small for single and multi-slice imperfection cases, while the influence is relatively large for half-span and full-span cases.In practical engineering, comprehensively considering the superimposed adverse influence of each single-factor imperfection forms, the reduction coefficient of segment ultimate loading coefficient is suggested as 0.80～0.85.