In order to explore the effect of hygrothermal coupling on the interfacial durability of steel structure strengthened with CFRP，the nano-material toughened epoxy adhesive developed by the team was used，the accelerated aging tests of adhesive colloid and CFRP-steel double lap joints were carried out for 30 days and 60 days under the water environment of 20℃，55℃and 70℃，respectively. The dynamic mechanical properties and tensile properties of adhesive colloid，and the shear properties of CFRP-steel double lap joints were tested after immersion. The test results were compared with those of non-immersed specimens. The influence of hygrothermal temperature and immersion time on the mechanical properties of adhesive and CFRP-steel double lap joints was revealed. The results show that the tensile strength and glass transition temperature of the adhesive decreased with the immersion time at the 20℃. After 60 days of immersion，the tensile strength and glass transition temperature decreased by 16.3% and 7.6℃ respectively. When the specimen is immersed at the 55℃ and 70℃ water for 30 days，tensile strength of the colloid changed little，glass transition temperature increased by 11.5℃. The tensile strength decreased by 27.8% after soaking in 70℃ water for 60 days. If the specimen is dipped in water at 20℃，55℃and 70℃ for 30 days，the ultimate load of CFRP-steel double-lap joints decreased by 2.13%，8.13% and 11.83%，respectively. The strength degradation of the joint is caused by the hygrothermal aging. The bonding strength of interface is degraded.