Abstract: The longitudinal joints of the segmental lining in pressurized water-conveyance tunnels are typically featured with detailed configurations such as double-row bolts, multiple waterproof measures, and edge gaps. Their flexural performance affects the overall mechanical response of the structure. To analyze the influence of detailed structural features on the flexural performance of the joint, this study constructed a joint flexural mechanical model, established the joint mechanical equilibrium equations based on the opening process, and verified the calculated results with the full-scale tests. The effects of edge gaps, bolts, and waterproof grooves arrangements on the flexural performance of the joint were emphatically analyzed. The results show that the bending moment-rotation curve of the joint presents an S-shaped distribution. The flexural stiffness of the joint exhibits an overall nonlinear attenuation trend as the joint opens. The presence of edge gaps reduces the initial flexural stiffness, while gap closure enhances the flexural performance. The ultimate flexural bearing capacity of the joint is optimal under a certain edge gap, with a more significant improvement under low axial force conditions. The double-row bolt arrangement significantly enhances the flexural performance on both sides of the joint. For example, under an axial force of 2MN, the positive and negative ultimate bending moments are increased by 215.0% and 91.6%, respectively, compared with the boltless scheme; the positive ultimate bending moment is increased by 120.5% compared with the outer single-row bolt scheme, and the negative ultimate bending moment is increased by 67.9% compared with the inner single-row bolt scheme. Adjusting the bolts properly toward the segment edge can improve the same-side flexural performance.