To investigate the effect of grouting to repair reflective cracking and chipping in asphalt pavements under humid conditions, optimizing the water resistance performance of a two-component polyurethane. The differences in grouting effectiveness under different interface conditions were characterized by mechanical tests using simulated crack specimens, and the effectiveness of water-resistant polyurethane grouting materials was also verified in conjunction with physical works. The results show that the strength recovery rate was very low under the wet interface, as the dry interface of the crack was more likely to enhance the grouting effect of the grout. However, adding ALT latent curing agent could improve strength recovery rates for grouting specimens under wet interface conditions. Good strength recovery rates were achieved with an ALT addition of 3%, which effectively improved interfacial bonding between grouting materials and cracks under wet environments.Bending settlements of pavements treated with reflective cracking are all close to those of normal pavements. Specifically, 28% reduction in flexural settlement in comparison to the diseased section; 23% increase in modulus of elasticity of the pavement after slurry treatment. Therefore, this grouting treatment technology effectively reduced the pavement's bending settlement, improved the pavement's resilience modulus and restored the pavement's structural stability. When repairing reflective cracks and grouting asphalt pavements, the rainy season should be avoided as much as possible, so that the cracks are in dry conditions to ensure the grout is effective, and waterproof polyurethane grout should be actively used when the inside of the pavement structure is wet.