Abstract: Cured-in-place-pipe (CIPP) lining is used to repair drainage pipes corroded by biological sulfuric acid and is also used in municipal sea drainage pipes. However, the durability of glass fiber reinforced methacrylate-based composite materials used in CIPP lining in sulfuric acid and seawater environments is unclear. This study established two aging conditions: 0.5% sulfuric acid and simulated seawater, with the temperature of 80℃ to accelerate aging. Pure water was used as a control. Characterization and testing methods such as water absorption test, three-point bending test, contact angle analysis, SEM, and FTIR were used for the study to evaluate the aging behavior of glass fiber reinforced methacrylate-based CIPP lining. The results show that the bending strength decreases by 57.9%, 58.4%, and 57.4% respectively, after accelerated aging in 0.5% sulfuric acid, simulated seawater, and pure water for 1440 h. While the bending modulus does not show a significant decrease. The hydroxyl group generated by the hydrolysis of the ester bond is partially oxidized to a carbonyl group, causing the resin to turn yellow after aging. Sulfuric acid deteriorates the resin surface and reduces the wettability, and also promotes water diffusion by corroding the surface glass fiber. The crystallization of salt in seawater hinders the diffusion of water and severely damages the resin layer on the material surface, leading to enhanced wettability. To enhance CIPP lining durability, efforts should focus on inhibiting moisture diffusion and degradation at the interface. This study can provide a reference basis for the durability evaluation of methacrylate used in CIPP repair materials.